Migrate backendSrv to getBackendSrv, fix direct DB connection

src/datasource-zabbix/zabbix/connectors/sql/sqlConnector.js

@@ -1,4 +1,5 @@
 import _ from 'lodash';
+import { getBackendSrv } from '@grafana/runtime';
 import { compactQuery } from '../../../utils';
 import mysql from './mysql';
 import postgres from './postgres';
@@ -17,8 +18,7 @@ export class SQLConnector extends DBConnector {
     this.sqlDialect = null;
 
     super.loadDBDataSource()
-    .then(ds => {
-      this.backendSrv = ds.backendSrv;
+    .then(() => {
       this.loadSQLDialect();
     });
   }
@@ -96,7 +96,7 @@ export class SQLConnector extends DBConnector {
       maxDataPoints: this.limit
     };
 
-    return this.backendSrv.datasourceRequest({
+    return getBackendSrv().datasourceRequest({
       url: '/api/tsdb/query',
       method: 'POST',
       data: {