Allow certificate_revocation to be set to true
Allow certificate_revocation to be set to true

The behavior before this patch is that even if you said:

    Migration::Config.new.set_certificate_revocation('true')

It would actually set it to false because the value "false" was hard
coded in all of the gsub! methods.  This patch fixes the issue by
actually substituting in the value provided to the method.

puppetlabs/puppetlabs-cve20113872,puppetlabs/puppetlabs-cve20113872