Fix SLMSnapshotBlockingIntegTests.testSnapshotInProgress (#49533)

This test must check for state `SUCCESS` as well. `SUCESS` in
`SnapshotsInProgress` means "all data nodes finished snapshotting sucessfully but master must still finalize the snapshot in the repo".
`SUCESS` does not mean that the snapshot is actually fully finished in this object.

You can easily reporduce the scenario in #49303 that has an in-progress snapshot in `SUCCESS` state
by waiting 20s before running the busy assert loop on the snapshot status so that all steps but the blocked
finalization can finish.

Closes #49303

x-pack/plugin/ilm/src/test/java/org/elasticsearch/xpack/slm/SLMSnapshotBlockingIntegTests.java

@@ -109,7 +109,8 @@ public class SLMSnapshotBlockingIntegTests extends ESIntegTestCase {
             SnapshotLifecyclePolicyItem.SnapshotInProgress inProgress = item.getSnapshotInProgress();
             assertThat(inProgress.getSnapshotId().getName(), equalTo(snapshotName));
             assertThat(inProgress.getStartTime(), greaterThan(0L));
-            assertThat(inProgress.getState(), anyOf(equalTo(SnapshotsInProgress.State.INIT), equalTo(SnapshotsInProgress.State.STARTED)));
+            assertThat(inProgress.getState(), anyOf(equalTo(SnapshotsInProgress.State.INIT), equalTo(SnapshotsInProgress.State.STARTED),
+                equalTo(SnapshotsInProgress.State.SUCCESS)));
             assertNull(inProgress.getFailure());
         });