Creating new ones (which is the implicit effect of FLAG_CANCEL_CURRENT)
causes PendingIntent.equals() to return false for the new and the old
instance, which in turn leads to AlarmManager failing to remove the
alarm.
Also remove the unneeded request code offsets. The intent actions for
the various actions are already distinct, so we need to only identify
between the intents that have the same actions; using the mailbox ID as
request code is sufficient for that purpose.
Change-Id: I9030c24a9c6b1c722b246601fde741f7027d3de7
