stackdriver: fix typescript errors

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

 import angular from 'angular';
 import _ from 'lodash';
 import * as options from './constants';
-import * as options from './constants';
 import kbn from 'app/core/utils/kbn';
 
 export class StackdriverAggregation {

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

@@ -418,6 +418,7 @@ function createTarget(existingFilters?: string[]) {
       name: '',
     },
     metricType: 'ametric',
+    service: '',
     refId: 'A',
     aggregation: {
       crossSeriesReducer: '',