need it for pipes too, and even if it isn't necessary it can't hurt.

In particular, on FreeBSD 11-CURRENT it seems pipes no longer wake up
from accept when closed in other threads, so let's deal with that before
FreeBSD 11 is released.

Reported by: Matthias Apitz <g u r u   a t   u n i x a r e a   d o t   d e>
Patch by: me
Tested by: Matthias Apitz <g u r u   a t   u n i x a r e a   d o t   d e>

(cherry picked from commit e18ecd4f)

Change-Id: I1b4c0438fbcc2ea53625f235906936fc1403e195