Add a notification channel for car services.

Notification channels are a feature that is being introduced in O. When
O is targetted, a corresponding notification channel needs to be
included with each notification.

Using the default notification channel because these notifications will
not be shown to the user during run time.

Remove the notification as a field in CanBusErrorNotifier because it's
not used in a release build; so, it's not necessary to keep around for
performance reasons.

Test: booted up on headunit and ensured no crashes
Bug: 38350550
Change-Id: I830bb3093331871ed7f1eaafa7684a79b4b1d310
2 files changed