In PR 227259, a user is reporting that they have code which is using
shutdown() to wakeup another thread blocked on a stream listen socket.
This code is failing, while it used to work on FreeBSD 10 and still
works on Linux.

It seems reasonable to add another exception to support something users are
actually doing, which used to work on FreeBSD 10, and still works on Linux.
And, it seems like it should be acceptable to POSIX, as we still return
ENOTCONN.

This patch is different to what had been committed to stable/11, since
code around listening sockets is different. Patch in D15019 is written
by jtl@, slightly modified by me.

PR: 227259
Obtained from: jtl
Approved by: re (kib)
Differential Revision: D15019