Reuse collected cluster state in EnrichPolicyRunner (#48488)

The cluster state is obtained twice in the EnrichPolicyRunner when updating 
the final alias. There is a possibility for the state to be slightly different 
between those two calls. This PR just has the function get the cluster state 
once and reuse it for the life of the function call.

Author: jbaiera

x-pack/plugin/enrich/src/main/java/org/elasticsearch/xpack/enrich/EnrichPolicyRunner.java

@@ -29,6 +29,7 @@
 import org.elasticsearch.action.admin.indices.settings.put.UpdateSettingsRequest;
 import org.elasticsearch.action.support.master.AcknowledgedResponse;
 import org.elasticsearch.client.Client;
+import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.AliasMetaData;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.metadata.MappingMetaData;
@@ -494,10 +495,9 @@ private void updateEnrichPolicyAlias(final String destinationIndexName) {
         String enrichIndexBase = EnrichPolicy.getBaseName(policyName);
         logger.debug("Policy [{}]: Promoting new enrich index [{}] to alias [{}]", policyName, destinationIndexName, enrichIndexBase);
         GetAliasesRequest aliasRequest = new GetAliasesRequest(enrichIndexBase);
-        String[] concreteIndices = indexNameExpressionResolver.concreteIndexNames(clusterService.state(), aliasRequest);
-        ImmutableOpenMap<String, List<AliasMetaData>> aliases = clusterService.state()
-            .metaData()
-            .findAliases(aliasRequest, concreteIndices);
+        ClusterState clusterState = clusterService.state();
+        String[] concreteIndices = indexNameExpressionResolver.concreteIndexNames(clusterState, aliasRequest);
+        ImmutableOpenMap<String, List<AliasMetaData>> aliases = clusterState.metaData().findAliases(aliasRequest, concreteIndices);
         IndicesAliasesRequest aliasToggleRequest = new IndicesAliasesRequest();
         String[] indices = aliases.keys().toArray(String.class);
         if (indices.length > 0) {