connection: fix dead-lock on policy-removal

connection: fix dead-lock on policy-removal

If we clear the policy-db on last kdbus_conn_unref(), we have to take the
policy semaphore. However, we allow calling kdbus_conn_unref() while
holding a connection lock. This might deadlock against normal policy-db
modifications.

Therefore, we move policy-setup _after_ kdbus_conn_connect() and ensure
the connection is active. Then we can move the policy-removal into
kdbus_conn_disconnect(), which itself must never be called while holding
any lock.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>