DATAREDIS-953 - Release connection after failed validation only once.

We now release a connection after a failed validation only once. Previously, a connection was released twice which caused a failure if the connection was obtained from a pool.

Original Pull Request: #445

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

@@ -1170,12 +1170,7 @@ public class LettuceConnectionFactory
 
 				if (!valid) {
 
-					if (connection != null) {
-						connectionProvider.release(connection);
-					}
-
 					log.warn("Validation of shared connection failed. Creating a new connection.");
-
 					resetConnection();
 					this.connection = getNativeConnection();
 				}