smbd: Separate aio_pthread indicator from normal EINTR

smbd: Separate aio_pthread indicator from normal EINTR

According to Posix and the Linux open(2) manpage, the open-syscall can
return EINTR. If that happens, core smbd saw this as an indication
that aio_pthread's open function was doing its job. With a real EINTR
without aio_pthread this meant we ended up in a server_exit after 20
seconds, because there was nobody to do the retry.

EINTR is mapped to NT_STATUS_RETRY. Handle this by just retrying after
a second.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=14285
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Thu Feb 20 22:14:25 UTC 2020 on sn-devel-184

(cherry picked from commit aebe427b77b5315eb5d2b05b8c72824ca0389723)