argos-systemd: stop watchdog while suspending on idle

argos-systemd: stop watchdog while suspending on idle

Systemd sometimes misdetected the watchdog while device goes to the suspend state.
If other process failed to suspend,
montonic time of systemd goes on although some process has been already frozen.
So when device woke up, systemd expired the watchdog timer of frozen process and killed it abnormally.

If argos-watchdog receives dbus signal about both suspend and resume,
it can stop and restart the watchdog timer.

Change-Id: Ied02df1e81cca21a05edbeb84f6746d612cc6b05
Signed-off-by: ByungSoo Kim <bs1770.kim@samsung.com>
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>