Elasticsearch: fix log row context erroring out (#31088) (#31094)

(cherry picked from commit c7e007d199)

Co-authored-by: Giordano Ricci <gio.ricci@grafana.com>

public/app/plugins/datasource/elasticsearch/datasource.ts

@@ -494,7 +494,7 @@ export class ElasticDatasource extends DataSourceApi<ElasticsearchQuery, Elastic
     });
     const payload = [header, esQuery].join('\n') + '\n';
     const url = this.getMultiSearchUrl();
-    const response = await this.post(url, payload);
+    const response = await this.post(url, payload).toPromise();
     const targets: ElasticsearchQuery[] = [{ refId: `${row.dataFrame.refId}`, metrics: [], isLogsQuery: true }];
     const elasticResponse = new ElasticResponse(targets, transformHitsBasedOnDirection(response, sort));
     const logResponse = elasticResponse.getLogs(this.logMessageField, this.logLevelField);