GH-210: Short-circuit Kinesis consumer for stop

Fixes https://github.com/spring-projects/spring-integration-aws/issues/210

To avoid extra cycles for tasks and locks renewal check for a closed shard
just after `getShardIterator()` request in a `NEW` consumer task

**Cherry-pick to `2.5.x`**

src/main/java/org/springframework/integration/aws/inbound/kinesis/KinesisMessageDrivenChannelAdapter.java

@@ -974,6 +974,10 @@ public class KinesisMessageDrivenChannelAdapter extends MessageProducerSupport
 														.amazonKinesis
 														.getShardIterator(shardIteratorRequest)
 														.getShardIterator();
+										if (this.shardIterator == null) {
+											// The shard is closed - stop consumer
+											this.state = ConsumerState.STOP;
+										}
 										if (ConsumerState.STOP != this.state) {
 											this.state = ConsumerState.CONSUME;
 										}