Tenant index migration was failing because KibanaMigrator import statement was commented.

Uncommenting that to resolve this issue.

Author: Shivang Doshi

lib/multitenancy/migrate_tenants.js

@@ -33,7 +33,7 @@ import _ from 'lodash';
 import Boom from 'boom';
 import elasticsearch from 'elasticsearch';
 import wrapElasticsearchError from './../backend/errors/wrap_elasticsearch_error';
-// import { KibanaMigrator } from '../../../../src/server/saved_objects/migrations';
+import { KibanaMigrator } from '../../../../src/server/saved_objects/migrations';
 
 async function migrateTenants (server) {