fix: close isAlive responses

F4SDM42WebApi/F4SDM42WebApiController.cs

@@ -398,7 +398,13 @@ namespace C4IT.F4SD
         [Route("isAlive"), HttpGet]
         public IHttpActionResult isAlive()
         {
-            return new StatusCodeResult(HttpStatusCode.NoContent);
+            var response = new HttpResponseMessage(HttpStatusCode.NoContent)
+            {
+                RequestMessage = Request
+            };
+            response.Headers.ConnectionClose = true;
+
+            return ResponseMessage(response);
         }
 
         [Route("loglevel"), HttpGet]