services: herd: Add a stop-service procedure.

* gnu/services/herd.scm (stop-service): New procedure.

gnu/services/herd.scm

@@ -49,7 +49,8 @@
             unload-services
             unload-service
             load-services
-            start-service))
+            start-service
+            stop-service))
 
 ;;; Commentary:
 ;;;
@@ -222,6 +223,10 @@ returns a shepherd <service> object."
   (with-shepherd-action name ('start) result
     result))
 
+(define (stop-service name)
+  (with-shepherd-action name ('stop) result
+    result))
+
 ;; Local Variables:
 ;; eval: (put 'alist-let* 'scheme-indent-function 2)
 ;; eval: (put 'with-shepherd 'scheme-indent-function 1)