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.

Unbreak this by removing all devices before releasing adapters map.
2 jobs for pr/bluetooth-fix-device-adapter-dependency-at-exit in 6 minutes and 5 seconds (queued for 10 seconds)
Status Name Job ID Coverage
  Container
passed build-container #14602285

00:04:29

 
  Build
passed build-meson #14602286

00:01:36