Adjust how snoozed alarms are rescheduled in response to TIME_SET,

TIMEZONE_CHANGED, and BOOT_COMPLETED.

Bug: 21363078

1. Dismiss snoozed alarms after a reboot
2. Do not reschedule snoozed alarms for their next scheduled instance;
keep the snoozed firing time. AlarmManager will immediately fire alarms
that are registered for already-passed times.

Change-Id: I64aa3d2c7a257bb140c06284c038c65f673b86e7