s3: auth: Move the declaration of struct dom_sid tmp_sid to function level scope.

s3: auth: Move the declaration of struct dom_sid tmp_sid to function level scope.

It's referred to outside of the {} brace scope it was defined in by
the following code:

            uid_to_unix_users_sid(*uid, &tmp_sid);
            user_sid = &tmp_sid;

As tmp_sid was going out of scope, user_sid was
being incorrectly set in the token sid list.

I think this *may* be the root cause of:

BUG: https://bugzilla.samba.org/show_bug.cgi?id=10618

But even if not this is an obvious error that must
be fixed.

Back-port from master: 1b3b89345480d16222da00753f973e36e2e0f92d

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(v4-2-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-2-test): Wed Jun  1 12:35:23 CEST 2016 on sn-devel-104