Use more reliable "never run" cron pattern in tests (#48608)

The cron schedule "1 2 3 4 5 ?" will run every May 4 at 03:02:01, which
may result in unnecessary test failures once a year. This commit
switches out uses of that schedule in tests for one which will never
execute (because it specifies a day which doesn't exist, Feb. 31). Also
factors the schedule out to a constant to make the intent clearer.

x-pack/plugin/ilm/qa/multi-node/src/test/java/org/elasticsearch/xpack/slm/SnapshotLifecycleRestIT.java

@@ -58,6 +58,7 @@ import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 import static org.hamcrest.Matchers.startsWith;
 
 public class SnapshotLifecycleRestIT extends ESRestTestCase {
+    private static final String NEVER_EXECUTE_CRON_SCHEDULE = "* * * 31 FEB ? *";
 
     @Override
     protected boolean waitForAllSnapshotsWiped() {
@@ -209,7 +210,7 @@ public class SnapshotLifecycleRestIT extends ESRestTestCase {
         // Create a snapshot repo
         initializeRepo(repoId);
 
-        createSnapshotPolicy(policyName, "snap", "1 2 3 4 5 ?", repoId, indexName, true);
+        createSnapshotPolicy(policyName, "snap", NEVER_EXECUTE_CRON_SCHEDULE, repoId, indexName, true);
 
         ResponseException badResp = expectThrows(ResponseException.class,
             () -> client().performRequest(new Request("POST", "/_slm/policy/" + policyName + "-bad/_execute")));
@@ -353,7 +354,7 @@ public class SnapshotLifecycleRestIT extends ESRestTestCase {
         initializeRepo(repoId);
 
         // Create a policy with a retention period of 1 millisecond
-        createSnapshotPolicy(policyName, "snap", "1 2 3 4 5 ?", repoId, indexName, true,
+        createSnapshotPolicy(policyName, "snap", NEVER_EXECUTE_CRON_SCHEDULE, repoId, indexName, true,
             new SnapshotRetentionConfiguration(TimeValue.timeValueMillis(1), null, null));
 
         // Manually create a snapshot
@@ -449,7 +450,7 @@ public class SnapshotLifecycleRestIT extends ESRestTestCase {
         // Create a snapshot repo
         initializeRepo("repo");
         // Create a policy with a retention period of 1 millisecond
-        createSnapshotPolicy("policy", "snap", "1 2 3 4 5 ?", "repo", "*", true,
+        createSnapshotPolicy("policy", "snap", NEVER_EXECUTE_CRON_SCHEDULE, "repo", "*", true,
             new SnapshotRetentionConfiguration(TimeValue.timeValueMillis(1), null, null));
         final String snapshotName = executePolicy("policy");
 

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

@@ -59,6 +59,7 @@ import static org.hamcrest.Matchers.greaterThan;
  */
 @ESIntegTestCase.ClusterScope(scope = ESIntegTestCase.Scope.TEST, numDataNodes = 0)
 public class SLMSnapshotBlockingIntegTests extends ESIntegTestCase {
+    private static final String NEVER_EXECUTE_CRON_SCHEDULE = "* * * 31 FEB ? *";
 
     static final String REPO = "my-repo";
     List<String> dataNodeNames = null;
@@ -88,7 +89,7 @@ public class SLMSnapshotBlockingIntegTests extends ESIntegTestCase {
         initializeRepo(REPO);
 
         logger.info("--> creating policy {}", policyName);
-        createSnapshotPolicy(policyName, "snap", "1 2 3 4 5 ?", REPO, indexName, true);
+        createSnapshotPolicy(policyName, "snap", NEVER_EXECUTE_CRON_SCHEDULE, REPO, indexName, true);
 
         logger.info("--> blocking master from completing snapshot");
         blockMasterFromFinalizingSnapshotOnIndexFile(REPO);
@@ -134,7 +135,7 @@ public class SLMSnapshotBlockingIntegTests extends ESIntegTestCase {
         initializeRepo(REPO);
 
         logger.info("--> creating policy {}", policyId);
-        createSnapshotPolicy(policyId, "snap", "1 2 3 4 5 ?", REPO, indexName, true,
+        createSnapshotPolicy(policyId, "snap", NEVER_EXECUTE_CRON_SCHEDULE, REPO, indexName, true,
             false, new SnapshotRetentionConfiguration(TimeValue.timeValueSeconds(0), null, null));
 
         // Create a snapshot and wait for it to be complete (need something that can be deleted)
@@ -261,7 +262,7 @@ public class SLMSnapshotBlockingIntegTests extends ESIntegTestCase {
         // Create a snapshot repo
         initializeRepo(REPO);
 
-        createSnapshotPolicy(policyId, "snap", "1 2 3 4 5 ?", REPO, indexName, true,
+        createSnapshotPolicy(policyId, "snap", NEVER_EXECUTE_CRON_SCHEDULE, REPO, indexName, true,
             partialSuccess, new SnapshotRetentionConfiguration(null, 1, 2));
 
         // Create a failed snapshot