fix elastic search test

Author: lunny

.drone.yml

@@ -45,6 +45,8 @@ services:
 
   - name: elasticsearch
     pull: default
+    environment:
+      - "discovery.type=single-node"
     image: elastic/elasticsearch:5.6.16
 
 steps:

integrations/mysql.ini.tmpl

@@ -11,7 +11,7 @@ SSL_MODE = disable
 
 [indexer]
 ISSUE_INDEXER_TYPE = elasticsearch
-ISSUE_INDEXER_CONN_STR = http://127.0.0.1:9200
+ISSUE_INDEXER_CONN_STR = http://elasticsearch:9200
 ISSUE_INDEXER_QUEUE_TYPE = noqueue
 ISSUE_INDEXER_PATH = integrations/indexers-mysql/issues.bleve
 REPO_INDEXER_ENABLED = true