Otherwise, if we do a very quick detach/attach, and the
after-state-change send_state() of the detach got delayed for some
reason, it may be processed after the new diskless->attaching state
change, probably confusing the peer.

Paranoia fix, not yet observed in real life.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>