Bugfix/trainvm 46

See: https://tickets.puppetlabs.com/browse/PUP-677
Puppet fails when the hostname, and thus the username on the master
  is set to all numerals.
I decided to apply the test to advanced as well, since although we
  don't manage the ssh_authorized_keys it is possible that something
  that relies on executing a command as a user might fail if we set
  the hostname and the username with all numeric characters.