Create admin user for person who did initial jenkins env setup

[patcon]

Currently, the admin needs to ensure that their user is in any github team used to generate the user databag. This is slightly error prone. It would make more sense to have either a) a default admin databag user, or b) dynamically add it during the vagrant run.

Either way, this user should probably have the public key that vagrant uses for the initial setup (the one sent to the new box).

[patcon]

Note that we're not currently disabling root logins via openssh, but would like to as soon as we figure out a good way to know when we're on the very first chef run. It would also suffice to know when root@IP_ADDRESS becomes unavailable, presumably after first run

[patcon]

cc: @anandpathaksharma