try to fix non-deterministic test (#3514)

js/server/tests/replication/replication-ongoing-global.js

@@ -899,6 +899,8 @@ function ReplicationOtherDBSuite() {
 
     // Now test if the Slave did replicate the new database...
     db._useDatabase(dbName);
+    // wait for collection to appear
+    waitUntil(function() { return (db._collection(cn) !== null); });
     assertEqual(50, collectionCount(cn), "The slave inserted the new collection data into the old one, it skipped the drop.");
     
     assertTrue(replication.globalApplier.state().state.running);