swaync-service-dispatcher: add -b to block on service state query, to avoid incorrect responses when run in parallel

hosts/common/programs/swaynotificationcenter/swaync-service-dispatcher

@@ -23,7 +23,7 @@ checkActive() {
     s6)
       # simulate a dry-run start. if no actions would be performed, then the service is up.
       # alternative is s6-svstat, but that doesn't support oneshots
-      test -z "$(s6-rc -n 0 start "$service")" && echo true || echo false
+      test -z "$(s6-rc -n 0 -b start "$service")" && echo true || echo false
       ;;
   esac
 }
@@ -34,7 +34,7 @@ startService() {
       /run/wrappers/bin/sudo systemctl start "$service"
       ;;
     s6)
-      s6-rc start "$service"
+      s6-rc -b start "$service"
       ;;
   esac
 }
@@ -45,7 +45,7 @@ stopService() {
       /run/wrappers/bin/sudo systemctl stop "$service"
       ;;
     s6)
-      s6-rc stop "$service"
+      s6-rc -b stop "$service"
       ;;
   esac
 }