Skip bwc versions without retention leases

Author: dnhatn

qa/full-cluster-restart/src/test/java/org/elasticsearch/upgrades/FullClusterRestartIT.java

@@ -1378,11 +1378,13 @@ public void testPeerRecoveryRetentionLeases() throws IOException {
      */
     public void testOperationBasedRecovery() throws Exception {
         if (isRunningAgainstOldCluster()) {
-            createIndex(index, Settings.builder()
+            final Settings.Builder settings = Settings.builder()
                 .put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
-                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 1)
-                .put(IndexSettings.INDEX_SOFT_DELETES_SETTING.getKey(), randomBoolean())
-                .build());
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 1);
+            if (getOldClusterVersion().onOrAfter(Version.V_6_7_0)) {
+                settings.put(IndexSettings.INDEX_SOFT_DELETES_SETTING.getKey(), randomBoolean());
+            }
+            createIndex(index, settings.build());
             ensureGreen(index);
             int committedDocs = randomIntBetween(100, 200);
             for (int i = 0; i < committedDocs; i++) {
@@ -1409,6 +1411,7 @@ public void testOperationBasedRecovery() throws Exception {
      * Verifies that once all shard copies on the new version, we should turn off the translog retention for indices with soft-deletes.
      */
     public void testTurnOffTranslogRetentionAfterUpgraded() throws Exception {
+        assumeTrue("requires soft-deletes and retention leases", getOldClusterVersion().onOrAfter(Version.V_6_7_0));
         if (isRunningAgainstOldCluster()) {
             createIndex(index, Settings.builder()
                 .put(IndexMetaData.INDEX_NUMBER_OF_SHARDS_SETTING.getKey(), 1)