Add optional config parameter to test elasticsearch endpoint. (#6877)

i18n/en.json

@@ -3547,6 +3547,10 @@
     "id": "ent.elasticsearch.test_config.license.error",
     "translation": "License does not support Elasticsearch."
   },
+  {
+    "id": "ent.elasticsearch.test_config.reenter_password",
+    "translation": "The Elasticsearch Server URL or Username has changed. Please re-enter the Elasticsearch password to test connection."
+  },
   {
     "id": "ent.emoji.licence_disable.app_error",
     "translation": "Custom emoji restrictions disabled by current license. Please contact your system administrator about upgrading your enterprise license."