enable useDeadLockChecker by default

Author: slandelle

src/main/java/com/ning/http/client/providers/netty/NettyAsyncHttpProviderConfig.java

@@ -97,7 +97,7 @@ public Set<Map.Entry<String, Object>> propertiesSet() {
     /**
      * Enable Netty DeadLockChecker
      */
-    private boolean useDeadLockChecker;
+    private boolean useDeadLockChecker = true;
 
     /**
      * Allow configuring the Netty's boss executor service.