Fix testRestoreIncreasesPrimaryTerms on 6.x (#38314)

In 6.x the open index request does not wait for shards to be active and
returns immediately. In this specific test, we want to capture the
values of the primary terms before the snapshot and restore and if it
does not wait for shard to be active the captured values might not be
up to date.

Closes #38223

server/src/test/java/org/elasticsearch/snapshots/SharedClusterSnapshotRestoreIT.java

@@ -3706,7 +3706,6 @@ public void testAbortedSnapshotDuringInitDoesNotStart() throws Exception {
         }
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/38223")
     public void testRestoreIncreasesPrimaryTerms() {
         final String indexName = randomAlphaOfLengthBetween(5, 10).toLowerCase(Locale.ROOT);
         createIndex(indexName, Settings.builder()
@@ -3719,7 +3718,7 @@ public void testRestoreIncreasesPrimaryTerms() {
             // open and close the index to increase the primary terms
             for (int i = 0; i < randomInt(3); i++) {
                 assertAcked(client().admin().indices().prepareClose(indexName));
-                assertAcked(client().admin().indices().prepareOpen(indexName));
+                assertAcked(client().admin().indices().prepareOpen(indexName).setWaitForActiveShards(ActiveShardCount.ONE));
             }
         }