bluetooth: Fix device->adapter dependency while releasing discovery

Change d7f95170 added a dependency on device
adapter pointer being valid while checking if bluetooth profile is supported by
device.

When adapter object is released, each device holding pointer to adapter being
released is notified to reset that to NULL. Since adapter objects are released
first when discovery object is unreferenced, each device will have adapter
pointer reset before the time device objects are released.

Fix observed crash by examining device adapter pointer. If it is NULL report
that device does not support any bluetooth profile instead of looking at UUIDs
supported by adapter.

Part-of: <pulseaudio/pulseaudio!646>
2 jobs for pr/bluetooth-fix-device-adapter-dependency-at-exit in 2 minutes and 58 seconds (queued for 4 seconds)