Fix X-Pack Indices Breaking Repository BwC Tests (#51120)

If some internal `.watcher` or so index gets created during these tests
then the shard counts on snapshot restores and creates won't match up with expectations.
Fixed by only creating the snapshot for the test index

Closes #50819

Author: original-brownbear

qa/repository-multi-version/src/test/java/org/elasticsearch/upgrades/MultiVersionRepositoryAccessIT.java

@@ -115,13 +115,14 @@ public void testCreateAndRestoreSnapshot() throws IOException {
         final String repoName = getTestName();
         try (RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(adminClient().getNodes().toArray(new Node[0])))) {
             final int shards = 3;
-            createIndex(client, "test-index", shards);
+            final String index = "test-index";
+            createIndex(client, index, shards);
             createRepository(client, repoName, false);
-            createSnapshot(client, repoName, "snapshot-" + TEST_STEP);
+            createSnapshot(client, repoName, "snapshot-" + TEST_STEP, index);
             final String snapshotToDeleteName = "snapshot-to-delete";
             // Create a snapshot and delete it right away again to test the impact of each version's cleanup functionality that is run
             // as part of the snapshot delete
-            createSnapshot(client, repoName, snapshotToDeleteName);
+            createSnapshot(client, repoName, snapshotToDeleteName, index);
             final List<Map<String, Object>> snapshotsIncludingToDelete = listSnapshots(repoName);
             // Every step creates one snapshot and we have to add one more for the temporary snapshot
             assertThat(snapshotsIncludingToDelete, hasSize(TEST_STEP.ordinal() + 1 + 1));
@@ -162,9 +163,10 @@ public void testReadOnlyRepo() throws IOException {
             final int shards = 3;
             final boolean readOnly = TEST_STEP.ordinal() > 1; // only restore from read-only repo in steps 3 and 4
             createRepository(client, repoName, readOnly);
+            final String index = "test-index";
             if (readOnly == false) {
-                createIndex(client, "test-index", shards);
-                createSnapshot(client, repoName, "snapshot-" + TEST_STEP);
+                createIndex(client, index, shards);
+                createSnapshot(client, repoName, "snapshot-" + TEST_STEP, index);
             }
             final List<Map<String, Object>> snapshots = listSnapshots(repoName);
             switch (TEST_STEP) {
@@ -196,11 +198,12 @@ public void testUpgradeMovesRepoToNewMetaVersion() throws IOException {
         final String repoName = getTestName();
         try (RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(adminClient().getNodes().toArray(new Node[0])))) {
             final int shards = 3;
-            createIndex(client, "test-index", shards);
+            final String index=  "test-index";
+            createIndex(client, index, shards);
             createRepository(client, repoName, false);
             // only create some snapshots in the first two steps
             if (TEST_STEP == TestStep.STEP1_OLD_CLUSTER || TEST_STEP == TestStep.STEP2_NEW_CLUSTER) {
-                createSnapshot(client, repoName, "snapshot-" + TEST_STEP);
+                createSnapshot(client, repoName, "snapshot-" + TEST_STEP, index);
                 final List<Map<String, Object>> snapshots = listSnapshots(repoName);
                 // Every step creates one snapshot
                 assertThat(snapshots, hasSize(TEST_STEP.ordinal() + 1));
@@ -211,10 +214,10 @@ public void testUpgradeMovesRepoToNewMetaVersion() throws IOException {
                 } else {
                     deleteSnapshot(client, repoName, "snapshot-" + TestStep.STEP1_OLD_CLUSTER);
                     ensureSnapshotRestoreWorks(client, repoName, "snapshot-" + TestStep.STEP2_NEW_CLUSTER, shards);
-                    createSnapshot(client, repoName, "snapshot-1");
+                    createSnapshot(client, repoName, "snapshot-1", index);
                     ensureSnapshotRestoreWorks(client, repoName, "snapshot-1", shards);
                     deleteSnapshot(client, repoName, "snapshot-" + TestStep.STEP2_NEW_CLUSTER);
-                    createSnapshot(client, repoName, "snapshot-2");
+                    createSnapshot(client, repoName, "snapshot-2", index);
                     ensureSnapshotRestoreWorks(client, repoName, "snapshot-2", shards);
                 }
             } else {
@@ -225,7 +228,7 @@ public void testUpgradeMovesRepoToNewMetaVersion() throws IOException {
                     expectThrowsAnyOf(expectedExceptions, () -> listSnapshots(repoName));
                     expectThrowsAnyOf(expectedExceptions, () -> deleteSnapshot(client, repoName, "snapshot-1"));
                     expectThrowsAnyOf(expectedExceptions, () -> deleteSnapshot(client, repoName, "snapshot-2"));
-                    expectThrowsAnyOf(expectedExceptions, () -> createSnapshot(client, repoName, "snapshot-impossible"));
+                    expectThrowsAnyOf(expectedExceptions, () -> createSnapshot(client, repoName, "snapshot-impossible", index));
                 } else {
                     assertThat(listSnapshots(repoName), hasSize(2));
                     if (TEST_STEP == TestStep.STEP4_NEW_CLUSTER) {
@@ -284,8 +287,8 @@ private static void createRepository(RestHighLevelClient client, String repoName
             is(true));
     }
 
-    private static void createSnapshot(RestHighLevelClient client, String repoName, String name) throws IOException {
-        client.snapshot().create(new CreateSnapshotRequest(repoName, name).waitForCompletion(true), RequestOptions.DEFAULT);
+    private static void createSnapshot(RestHighLevelClient client, String repoName, String name, String index) throws IOException {
+        client.snapshot().create(new CreateSnapshotRequest(repoName, name).waitForCompletion(true).indices(index), RequestOptions.DEFAULT);
     }
 
     private void createIndex(RestHighLevelClient client, String name, int shards) throws IOException {