vm/systemd: force exit status 0 in qubes-sysinit

If /rw/config/rc.local-early does not exits, exit status is incorrectly 1.

vm-systemd/qubes-sysinit.sh

@@ -72,3 +72,4 @@ fi
 
 [ -x /rw/config/rc.local-early ] && /rw/config/rc.local-early
 
+exit 0