Remove prod8 from production

This is as it will be running Ubuntu Trusty and will be running
HHVM not what we currently use for prod4. So annoying to maintain
for ansible.
Remove denyhosts

Causes failures for Ubuntu and no real use for it. @addshore: worth
an apt --purge of this or not?
specify port for ubuntu
remove useless php crontab
add base hhvm role
Create mediawiki group