Add missing lock in reschedulign service restart

                // Since we kicked off all its pending restarts, there could be some open slots

                // in the pending restarts list, schedule a check on it. We are posting to the same

                // handler, so by the time of the check, those immediate restarts should be done.

                mAm.mHandler.post(() ->

                mAm.mHandler.post(() -> {

                    final long now = SystemClock.uptimeMillis();

                    synchronized (mAm) {

                        rescheduleServiceRestartIfPossibleLocked(

                                getExtraRestartTimeInBetweenLocked(),

                                mAm.mConstants.SERVICE_MIN_RESTART_TIME_BETWEEN,

                                "other", SystemClock.uptimeMillis())

                );

                                "other", now);

                    }

                });

            }

        }

        return didSomething;