Feature request: Force a particular region and disable the region picker

[jimmyduty]

Hello and thanks for the great project!

My team has a Nomad cluster federated between two AWS regions. Because of this issue, we are running a copy of hashi-ui in each region, on different subdomains. We'd like to be to disable the region picker part of the UI and have the root path automatically redirect to the path for the region that copy of hashi-ui is running in.

I'd open a PR for this myself, but I haven't done much front end work in a long time and don't know React nearly well enough. I might be able to do it with some guidance on what needs to be changed. Any back end changes shouldn't be an issue.

Thanks much!

[jippi]

I've responded in #385