ofproto: Remove ->timeout_mutex from struct rule (just use ->mutex).

ofproto: Remove ->timeout_mutex from struct rule (just use ->mutex).

I think that ->timeout_mutex and ->mutex were separate because the latter
(which was actually a rwlock named ->rwlock until recently) was held for
long periods of time, which meant that having a separate ->timeout_mutex
reduced lock contention.  But ->mutex is now only held briefly, so it seems
reasonable to just use it.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>