bdrv_open_inherit() calls several functions for which it needs to hold
the AioContext lock, but currently doesn't. This includes calls in
bdrv_append_temp_snapshot(), for which bdrv_open_inherit() is the only
caller. Fix the locking in these places.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230605085711.21261-8-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>