Settings: fix quiet hours

http://jira.omnirom.org/browse/OMNI-627

Change-Id: Ica3bff10b3147120593bbe688882404625df18be
Settings: fix QuietHour start time

when user decide when quiethour will start/stop using time preference
alarm manager will setup the time, and call stop service in many times
before starting the service

this add some check to prevent call stop service before time to start

fix http://jira.omnirom.org/browse/OMNI-595

Change-Id: Ide4cb7f651ab153e1738d309992628b951e551c1