DATAREDIS-971 - Fix BitFieldType initialization through BitFieldSubCommands.signed().

We now initialize with the correct signed preference.

Original pull request: #447.

src/main/java/org/springframework/data/redis/connection/BitFieldSubCommands.java

@@ -447,7 +447,7 @@ public class BitFieldSubCommands implements Iterable<BitFieldSubCommand> {
 		 * @return
 		 */
 		public static BitFieldType signed(int bits) {
-			return new BitFieldType(false, bits);
+			return new BitFieldType(true, bits);
 		}
 
 		/**