Fix exit sequence

Fix exit sequence

root@localhost:~# systemctl stop feedbackd.service
root@localhost:~# systemctl status feedbackd
* feedbackd.service - System Vibrator Daemon
   Loaded: loaded (/usr/lib/systemd/system/feedbackd.service; disabled; vendor preset: enabled)
   Active: inactive (dead) since Mon 2018-08-13 08:11:48 KST; 4s ago
  Process: 804 ExecStart=/usr/bin/feedbackd (code=exited, status=0/SUCCESS)
 Main PID: 804 (code=exited, status=0/SUCCESS)

Aug 13 08:11:47 localhost systemd[1]: Stopping System Vibrator Daemon...
Aug 13 08:11:48 localhost feedbackd[804]: g_main_loop_unref: assertion 'loop != NULL' failed
Aug 13 08:11:48 localhost systemd[1]: Stopped System Vibrator Daemon.
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

Change-Id: I24178f135688a8cb5cec55c602baf79853ed37cb
Signed-off-by: Hyotaek Shim <hyotaek.shim@samsung.com>