connectionmanager: announce non ready channel on shutdown

This is useful for the conversation_module if any channel is pending
while shutting down, as the previous fetch status was not updated.
More generally, every connectDevice() should call the associated
callback.

Add a unit test to replicate this scenario.

Change-Id: I72f2975dc15dd4bac3f55c2f899ebb1ae5a7a7f3