修复Prometheus连接错误的问题

server/prometheus-service.js

@@ -6,8 +6,12 @@ const QUERY_TIMEOUT = 10000;
  * Create an axios instance for a given Prometheus URL
  */
 function createClient(baseUrl) {
+  let url = baseUrl.replace(/\/+$/, '');
+  if (!/^https?:\/\//i.test(url)) {
+    url = 'http://' + url;
+  }
   return axios.create({
-    baseURL: baseUrl.replace(/\/+$/, ''),
+    baseURL: url,
     timeout: QUERY_TIMEOUT
   });
 }