do not fall back to local username for ssh user
do not fall back to local username for ssh user

The Vagrant instances will always use "vagrant" for
username, whether VirtualBox or DigitalOcean. In production,
admin should provide the username in prod-specific.yml
and on the command-line. Additionally, in a Tails instance
the username would be "amnesia", which should not be the
admin user on the prod servers.

mark-in/securedrop-prov-upstream,mark-in/securedrop-prov-upstream,mark-in/securedrop-prov-upstream,mark-in/securedrop-prov-upstream