generate unique id when variable is multi

public/app/plugins/datasource/cloudwatch/datasource.ts

@@ -404,8 +404,10 @@ export default class CloudWatchDatasource {
       scopedVar[variable.name] = v;
       t.refId = target.refId + '_' + v.value;
       t.dimensions[dimensionKey] = templateSrv.replace(t.dimensions[dimensionKey], scopedVar);
-      if (target.id) {
+      if (variable.multi && target.id) {
         t.id = target.id + window.btoa(v.value).replace(/=/g, '0'); // generate unique id
+      } else {
+        t.id = target.id;
       }
       return t;
     });