BUG/MINOR: haproxy: don't wake already stopping threads on exit

Commit d645574 ("MINOR: soft-stop: let the first stopper only signal
other threads") introduced a minor mistake which is that when a stopping
thread signals all other threads, it also signals itself. When
single-threaded, the process constantly wakes up while waiting for
last connections to exit. Let's reintroduce the lost mask to avoid
this.

No backport is needed, this is 2.2-dev only.
1 file changed