Bug 867649 - Switch the SMS app from using the high-priority wake lock to the CPU wake lock.

Without this patch, I think it's possible for us not to notify the user
of an incoming SMS, failing for the same reason that we sometimes don't
ring alarms: The device goes to sleep before we play the sound.
Merge pull request #9499 from jlebar/sms-use-cpu-lock

Bug 867649 - Switch the SMS app from using the high-priority wake lock t...