Restructure MPM disabling
Restructure MPM disabling

This takes the approach of listing the disabling steps once rather than
repeating it for every mpm.

I wasn't quite sure on the prefork disabling. Does prefork need to stay
enabled for itk?

traylenator/puppetlabs-apache,traylenator/puppetlabs-apache,puppetlabs/puppetlabs-apache,puppetlabs/puppetlabs-apache