Add UPDATE_ACTION to Gservices, used by the new checkin service.

        public static final String OVERRIDE_ACTION =

            "com.google.gservices.intent.action.GSERVICES_OVERRIDE";

        /**

         * Intent action to set Gservices with new values.  (Requires WRITE_GSERVICES permission.)

         */

        @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)

        public static final String UPDATE_ACTION =

            "com.google.gservices.intent.action.GSERVICES_UPDATE";

        private static volatile NameValueCache mNameValueCache = null;

        private static final Object mNameValueCacheLock = new Object();