DO NOT MERGE: Maintain binding to crashed listeners.

Adapted from change I44ce250e, "Maintain binding to crashed
listeners from NotificationManagerService.":

> This fixes the logic on the death handlers for notification
> listeners, and doesn't unbind from the listener services so
> that the system will bring them back up again.

Bug: 12587702
Change-Id: I41d0c6733046ee9760bcfae4407e754592b805ea