stackdriver: fix failing tests

public/app/plugins/datasource/stackdriver/datasource.ts

@@ -200,11 +200,9 @@ export default class StackdriverDatasource {
         message = error;
       } else {
         message = 'Stackdriver: ';
-        message += error.statusText ? error.statusText + ': ' : '';
+        message += error.statusText ? error.statusText : defaultErrorMessage;
         if (error.data && error.data.error && error.data.error.code) {
-          message += error.data.error.code + '. ' + error.data.error.message;
-        } else {
-          message = defaultErrorMessage;
+          message += ': ' + error.data.error.code + '. ' + error.data.error.message;
         }
       }
     } finally {

public/app/plugins/datasource/stackdriver/specs/datasource.test.ts

@@ -6,7 +6,7 @@ import { TemplateSrvStub } from 'test/specs/helpers';
 describe('StackdriverDataSource', () => {
   const instanceSettings = {
     jsonData: {
-      projectName: 'testproject',
+      defaultProject: 'testproject',
     },
   };
   const templateSrv = new TemplateSrvStub();
@@ -54,7 +54,7 @@ describe('StackdriverDataSource', () => {
             Promise.reject({
               statusText: 'Bad Request',
               data: {
-                error: JSON.stringify({ error: { code: 400, message: 'Field interval.endTime had an invalid value' } }),
+                error: { code: 400, message: 'Field interval.endTime had an invalid value' },
               },
             }),
         };