Get replicaSet using os.getenv()

- Previously we assumed all environments would have a replicaset called 'production'
- This broke ci-new when it attemped to attach to a different set
- Adding in the variable allows us to override the value of the replicaset in various jenkins jobs

![](https://24.media.tumblr.com/01284a87ef836997aadf521a5b9104f1/tumblr_mzwx6bA3zp1tpnsujo1_500.jpg)