fix(OpenTSDB): correct content-type, fixes #4965

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

@@ -129,11 +129,6 @@ function (angular, _, dateMath) {
       };
 
       this._addCredentialOptions(options);
-
-      // 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);
     };
 

public/app/plugins/panel/graph/graph.js

@@ -251,11 +251,14 @@ function (angular, $, moment, _, kbn, GraphTooltip) {
           function callPlot(incrementRenderCounter) {
             try {
               $.plot(elem, sortedSeries, options);
-              delete ctrl.error;
-              delete ctrl.inspector;
+              if (ctrl.renderError) {
+                delete ctrl.error;
+                delete ctrl.inspector;
+              }
             } catch (e) {
               console.log('flotcharts error', e);
               ctrl.error = e.message || "Render Error";
+              ctrl.renderError = true;
               ctrl.inspector = {error: ctrl.error};
             }