Delete unsed mDnsLock.

Bug: 21449922
Change-Id: I0c9f95c30eaa170d809e86f6505379f34a0a7603
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 6f7e1a4..e07e4e2 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -199,7 +199,6 @@
     // 0 is full bad, 100 is full good
     private int mDefaultInetConditionPublished = 0;
 
-    private Object mDnsLock = new Object();
     private int mNumDnsEntries;
 
     private boolean mTestMode;