Using correct default shard prioritization strategy.

* Fixing bug where this was set as default in configuration, but if a
configuraiton is not specified it falls back to parent prioritization.

src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/Worker.java

@@ -1469,7 +1469,7 @@ public class Worker implements Runnable {
             }
 
             if (shardPrioritization == null) {
-                shardPrioritization = new ParentsFirstShardPrioritization(1);
+                shardPrioritization = new NoOpShardPrioritization();
             }
 
             if (kinesisProxy == null) {