Refs #7077/BZ1127242: generate random password for pulp user.

Generate a random password instead of using the password "admin"
for the default pulp user.

http://projects.theforeman.org/issues/7077
https://bugzilla.redhat.com/show_bug.cgi?id=1127242
You'll want to do something like - https://github.com/Katello/puppet-katello/blob/master/manifests/params.pp#L48