s3:unix_msg: don't fill cmsg buffer in unix_dgram_send_job()

s3:unix_msg: don't fill cmsg buffer in unix_dgram_send_job()

Do this in queue_msg, instead.
This renders unix_dgram_send_job() as simple as it was before
we introduced fd-passing -- as it is intended.

This also changes struct unix_dgram_msg to not contain
the fd-array, but the correspondingly filled msghdr and cmsg buf.

Pair-Programmed-With: Volker Lendecke <vl@samba.org>
Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Michael Adam <obnox@samba.org>
Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>