Add edit and delete buttons to zen rules

Test: atest ZenModeScheduleRuleSettingsTest ZenModeEventRuleSettingsTest
Test: manual
Bug: 111475013
Fixes: 120787343
Fixes: 120758763
Change-Id: If81ce2972e6887fb2a85d4b7262e81b26162e19c

src/com/android/settings/notification/ZenModeSettingsBase.java

@@ -52,9 +52,14 @@ abstract public class ZenModeSettingsBase extends RestrictedDashboardFragment {
     }
 
     @Override
-    public void onCreate(Bundle icicle) {
-        mContext = getActivity();
+    public void onAttach(Context context) {
+        super.onAttach(context);
+        mContext = context;
         mBackend = ZenModeBackend.getInstance(mContext);
+    }
+
+    @Override
+    public void onCreate(Bundle icicle) {
         super.onCreate(icicle);
         updateZenMode(false /*fireChanged*/);
     }