Do not dismiss snoozed alarms upon superficial updates.

Bug: 21470985

Superficial updates are changes that do not affect firing time of an
alarm such as label, ringtone, and vibration changes.
Repeat pattern, enable/disable, and time changes are major updates,
for which snoozed alarms will still be dismissed.

Change-Id: I3c2017eddedba995d60892c004423eb8de015bb2