DATAREDIS-257 - Shutdown the client when DefaultLettucePool is destroyed.

DefaultLettucePool manages a RedisClient instance that's created
when afterPropertiesSet is called. The client was not being shutdown
as part of the pool's destroy() processing leading to a resource leak.
On OS X this would manifest itself as a growing number of kqueue file
descriptors being consumed eventually leading to a failure when
something tries to get a file descriptor and is unable to do so.

This commit updates destroy() to call the client's shutdown() method.

Original pull request: #26

src/main/java/org/springframework/data/redis/connection/lettuce/DefaultLettucePool.java

@@ -114,6 +114,7 @@ public class DefaultLettucePool implements LettucePool, InitializingBean {
 
 	public void destroy() {
 		try {
+			client.shutdown();
 			internalPool.close();
 		} catch (Exception e) {
 			throw new PoolException("Could not destroy the pool", e);