service: keep a pending reload across a second conf reload

A service whose condition goes into flux during a reload is paused
with its reload still pending.  If another reload was requested in
the meantime, re-parsing its unchanged .conf file cleared the pending
mark, so the service was resumed without ever being reloaded.  Seen
with sshd <pid/syslogd> on Infix, where a configuration change that
touched both landed as two reloads in a row and sshd kept its old
listen addresses.

The mark is only ever cleared once the change has been applied, so a
mark that is still set when the file is parsed again means exactly
that: not applied yet.  Leave it alone.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/service.c

@@ -2703,11 +2703,14 @@ svc_t *service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 	if (cgroup)
 		parse_cgroup(svc, cgroup);
 
-	/* New, recently modified or unchanged ... used on reload. */
+	/*
+	 * New or modified since the last reload.  The mark is cleared when
+	 * the change has been applied, on start or reload, so one that is
+	 * still set here is a change that has not been applied yet, e.g.
+	 * the service is paused waiting for a condition.  Leave it.
+	 */
 	if ((file && conf_changed(file)) || conf_changed(svc_getenv(svc)) || svc->args_dirty)
 		svc_mark_dirty(svc);
-	else
-		svc_mark_clean(svc);
 
 	svc_enable(svc);