tmpfiles: do not process systemd.conf

This file contains definitions specific to systemd, so we should not
process it.

Reported-by: <andrew.gregory.8@gmail.com>

sh/tmpfiles.sh.in

@@ -201,6 +201,7 @@ tmpfiles_d=''
 # `/run/tmpfiles/foo.conf' will always be read after `/etc/tmpfiles.d/bar.conf'
 for d in ${tmpfiles_dirs} ; do
 	[ -d $d ] && for f in ${d}/*.conf ; do
+		[ "$f" = "$d/systemd.conf" ] && continue
 		[ -f $f ] && tmpfiles_basenames="${tmpfiles_basenames}\n${f##*/}"
 	done # for f in ${d}
 done # for d in ${tmpfiles_dirs}