Test awaits Lucene snapshot upgrade

This commit marks OldIndexBackwardsCompatibilityIT#testOldIndexes as
awaiting a Lucene snapshot upgrade to reflect the fact that
Elasticsearch 2.2.0 is built against Lucene 5.4.1 but the current Lucene
snapshot in master/2.x does not contain the Lucene version 5.4.1 field.

Relates #16373

core/src/test/java/org/elasticsearch/bwcompat/OldIndexBackwardsCompatibilityIT.java

@@ -279,6 +279,7 @@ public class OldIndexBackwardsCompatibilityIT extends ESIntegTestCase {
         }
     }
 
+    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/16373")
     public void testOldIndexes() throws Exception {
         setupCluster();