systemd: local-d.service improvements.

1- Enable it by default but give a chance to also disable it.
2- Rather than passing ACTION via envvar, pass it as first argument in run-parts.

srcpkgs/systemd/files/local-d.service

@@ -3,8 +3,8 @@ Description=/etc/local.d execution
 
 [Service]
 Type=oneshot
-ExecStart=/usr/bin/env -i ACTION=start /usr/bin/run-parts /etc/local.d
-ExecStop=/usr/bin/env -i ACTION=stop /usr/bin/run-parts --reverse /etc/local.d
+ExecStart=/usr/bin/run-parts --arg="start" /etc/local.d
+ExecStop=/usr/bin/run-parts --arg="stop" --reverse /etc/local.d
 TimeoutSec=0
 RemainAfterExit=yes