Make mPermissionMonitor in ConnectivityService private

Since mPermissionMonitor is not used from test now.

Test: m
Change-Id: I049274023d60c8a04fccae9b6cf5cac03dd4878e
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index df29b8e..eef4a0e 100755
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -408,8 +408,7 @@
 
     private final MockableSystemProperties mSystemProperties;
 
-    @VisibleForTesting
-    protected final PermissionMonitor mPermissionMonitor;
+    private final PermissionMonitor mPermissionMonitor;
 
     @VisibleForTesting
     final RequestInfoPerUidCounter mNetworkRequestCounter;