INT-4126: Fix Redis lock to use SET NX EX

JIRA: https://jira.spring.io/browse/INT-4126

Looks like `WATCH` doesn't provide good isolation when the call is performed concurrently at the same time from different Threads.

* Change locking algorithm as it is recommended by Redis `SET` command: http://redis.io/commands/set:
```
SET resource-name anystring NX EX max-lock-time
```

* Add `@Repeat(10)` to the `AggregatorWithRedisLocksTests#testDistributedAggregator()` since that helped to reproduce the issue

**Cherry-pick to 4.3.x & 4.2.x**

spring-integration-redis/src/test/java/org/springframework/integration/redis/util/AggregatorWithRedisLocksTests.java

@@ -46,11 +46,13 @@ import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.PollableChannel;
 import org.springframework.messaging.support.GenericMessage;
 import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.annotation.Repeat;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
 /**
  * @author Gary Russell
+ * @author Artem Bilan
  * @since 4.0
  *
  */
@@ -125,6 +127,7 @@ public class AggregatorWithRedisLocksTests extends RedisAvailableTests {
 
 	@Test
 	@RedisAvailable
+	@Repeat(10)
 	public void testDistributedAggregator() throws Exception {
 		this.releaseStrategy.reset(1);
 		Executors.newSingleThreadExecutor().execute(asyncSend("foo", 1, 1));
@@ -223,5 +226,7 @@ public class AggregatorWithRedisLocksTests extends RedisAvailableTests {
 			this.callers = new AtomicInteger();
 			this.maxCallers = new AtomicInteger();
 		}
+
 	}
+
 }