Pull alpine image in a retry in Docker tests (#88654)

Closes #88651. When using an `alpine` image to perform container
fiddling, first explicitly pull the image and do so in a loop, in an
attempt to make things more robust.

Author: pugnascotia

qa/os/src/test/java/org/elasticsearch/packaging/util/docker/Docker.java

@@ -347,6 +347,9 @@ public static Path findInContainer(Path base, String type, String pattern) throw
      * @param containerPath The path to mount localPath inside the container.
      */
     private static void executePrivilegeEscalatedShellCmd(String shellCmd, Path localPath, Path containerPath) {
+        final String image = "alpine:3.13";
+        ensureImageIsPulled(image);
+
         final List<String> args = new ArrayList<>();
 
         args.add("docker run");
@@ -358,7 +361,7 @@ private static void executePrivilegeEscalatedShellCmd(String shellCmd, Path loca
         args.add("--volume \"" + localPath.getParent() + ":" + containerPath.getParent() + "\"");
 
         // Use a lightweight musl libc based small image
-        args.add("alpine:3.13");
+        args.add(image);
 
         // And run inline commands via the POSIX shell
         args.add("/bin/sh -c \"" + shellCmd + "\"");
@@ -368,6 +371,33 @@ private static void executePrivilegeEscalatedShellCmd(String shellCmd, Path loca
         sh.run(command);
     }
 
+    private static void ensureImageIsPulled(String image) {
+        // Don't pull if the image already exists. This does also mean that we never refresh it, but that
+        // isn't an issue in CI.
+        if (sh.runIgnoreExitCode("docker image inspect -f '{{ .Id }}' " + image).isSuccess()) {
+            return;
+        }
+
+        Shell.Result result = null;
+        int i = 0;
+        while (true) {
+            result = sh.runIgnoreExitCode("docker pull " + image);
+            if (result.isSuccess()) {
+                return;
+            }
+
+            if (++i == 3) {
+                throw new RuntimeException("Failed to pull Docker image [" + image + "]: " + result);
+            }
+
+            try {
+                Thread.sleep(10_000L);
+            } catch (InterruptedException e) {
+                // ignore
+            }
+        }
+    }
+
     /**
      * Create a directory with specified uid/gid using Docker backed privilege escalation.
      * @param localPath The path to the directory to create.