Evergreen does not currently have a mechanism for updating its own distribution code once running.  We need a way to be able to push updates to clients so they can receive the latest version of the Evergreen client without having to redeploy the docker container.

The plan is to have the client create a versioned distributable tarball that contains everything needed to upgrade the client. 

Goals:

• The client would receive the url to the latest version of Evergreen as part of the updates response
• The client would download the versioned tarball to a directory and initiate self restart
• The startup script would be responsible for checking the directory to see if there's a new version of the client and replacing the files
• The startup script will also be responsible for rolling back to a previous version if the client does not startup - considering using versioned symlinks to handle versioning and rollback.