On reload/restart we must wait for services to stop first

This patch adds support for declaring *why* a service is being stopped
or reloaded.  This is later used when all stopped services have been
collected by the `service_monitor()` to issue start or postponed SIGHUP.

As an added benefit we can now also see why a service is not running.
If it has been paused by a user, halted when moving to another runlevel,
waiting for a condition (event), or similar.

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

sig.c

@@ -96,6 +96,7 @@ void do_shutdown(int sig)
  */
 static void sighup_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
 {
+	/* INIT_CMD_RELOAD: 'init q', 'initctl reload', and SIGHUP */
 	service_reload_dynamic();
 }