Fix the clock resolution to millis in GetWatchResponseTests (#38405)

the clock resolution changed from jdk8->jdk10, hence the test is passing
in jdk8 but failing in jdk10. The Watcher's objects are serialised and
deserialised with milliseconds precision, making test to fail in jdk 10
and higher

closes #38400

Author: pgomulka

x-pack/plugin/core/src/test/java/org/elasticsearch/protocol/xpack/watcher/GetWatchResponseTests.java

@@ -23,6 +23,8 @@
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.time.Clock;
+import java.time.Instant;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
 import java.util.Collections;
@@ -124,15 +126,15 @@ private static BytesReference simpleWatch() {
 
     private static WatchStatus randomWatchStatus() {
         long version = randomLongBetween(-1, Long.MAX_VALUE);
-        WatchStatus.State state = new WatchStatus.State(randomBoolean(), ZonedDateTime.now(ZoneOffset.UTC));
+        WatchStatus.State state = new WatchStatus.State(randomBoolean(), nowWithMillisResolution());
         ExecutionState executionState = randomFrom(ExecutionState.values());
-        ZonedDateTime lastChecked = rarely() ? null : ZonedDateTime.now(ZoneOffset.UTC);
-        ZonedDateTime lastMetCondition = rarely() ? null : ZonedDateTime.now(ZoneOffset.UTC);
+        ZonedDateTime lastChecked = rarely() ? null : nowWithMillisResolution();
+        ZonedDateTime lastMetCondition = rarely() ? null : nowWithMillisResolution();
         int size = randomIntBetween(0, 5);
         Map<String, ActionStatus> actionMap = new HashMap<>();
         for (int i = 0; i < size; i++) {
             ActionStatus.AckStatus ack = new ActionStatus.AckStatus(
-                ZonedDateTime.now(ZoneOffset.UTC),
+                nowWithMillisResolution(),
                 randomFrom(ActionStatus.AckStatus.State.values())
             );
             ActionStatus actionStatus = new ActionStatus(
@@ -152,16 +154,16 @@ private static WatchStatus randomWatchStatus() {
     }
 
     private static ActionStatus.Throttle randomThrottle() {
-        return new ActionStatus.Throttle(ZonedDateTime.now(ZoneOffset.UTC), randomAlphaOfLengthBetween(10, 20));
+        return new ActionStatus.Throttle(nowWithMillisResolution(), randomAlphaOfLengthBetween(10, 20));
     }
 
     private static ActionStatus.Execution randomExecution() {
         if (randomBoolean()) {
             return null;
         } else if (randomBoolean()) {
-            return ActionStatus.Execution.failure(ZonedDateTime.now(ZoneOffset.UTC), randomAlphaOfLengthBetween(10, 20));
+            return ActionStatus.Execution.failure(nowWithMillisResolution(), randomAlphaOfLengthBetween(10, 20));
         } else {
-            return ActionStatus.Execution.successful(ZonedDateTime.now(ZoneOffset.UTC));
+            return ActionStatus.Execution.successful(nowWithMillisResolution());
         }
     }
 
@@ -227,4 +229,8 @@ private static ActionStatus.Execution convertHlrcToInternal(org.elasticsearch.cl
     private static ActionStatus.Throttle convertHlrcToInternal(org.elasticsearch.client.watcher.ActionStatus.Throttle throttle) {
         return new ActionStatus.Throttle(throttle.timestamp(), throttle.reason());
     }
+
+    private static ZonedDateTime nowWithMillisResolution() {
+        return Instant.ofEpochMilli(Clock.systemUTC().millis()).atZone(ZoneOffset.UTC);
+    }
 }