fixed typo for elasticsearch url

ISSUE:
```
I1014 19:40:51.128684 16130 es.go:137] elasticsearch container started, browser at %s/_plugin/head/http://localhost:9200
```

DEMO:
```
I1014 20:09:47.607432 26308 es.go:137] elasticsearch container started, browser at http://localhost:9200/_plugin/head/
```