Fix incomplete app termination

When dismissing the task from the recents list, the app would go
away but the service would stay up. Relaunching the app would
then complete the termination and result in a second shutdown.

Stop the service on task removal to avoid the weird double-start
artifact.

Ref CRACKLING-1025

Change-Id: I3bc3be75501294da4a526f0634149449f645edc2