fix: return no content healthcheck result

F4SDM42WebApi/F4SDM42WebApiController.cs

@@ -466,9 +466,9 @@ namespace C4IT.F4SD
         }
 
         [Route("isAlive"), HttpGet]
-        public bool isAlive()
+        public IHttpActionResult isAlive()
         {
-            return true;
+            return new StatusCodeResult(HttpStatusCode.NoContent);
         }
 
         [Route("loglevel"), HttpGet]