If OpenTSDB is 3rd-party hosted (or by another team) and does not support OPTIONS, send the request as POST (urlencoded)

public/app/plugins/datasource/opentsdb/datasource.js

@@ -72,6 +72,9 @@ function (angular, _, dateMath) {
         data: reqBody
       };
 
+      // In case the backend is 3rd-party hosted and does not suport OPTIONS, urlencoded requests
+      // go as POST rather than OPTIONS+POST
+      options.headers = { 'Content-Type': 'application/x-www-form-urlencoded' };
       return backendSrv.datasourceRequest(options);
     };