Remove some vagrant nodesets

Replacements are based on beaker-hostgenerator. To generate them as
static files:

  beaker-hostgenerator -t vagrant <spec>

To generate them on the fly when running beaker:

  BEAKER_setfile=<spec>{hypervisor=vagrant}

Users of vagrant_libvirt can also specify it as hypervisor.

moduleroot/spec/acceptance/nodesets/centos-6-x64.yml.erb
  centos6-64
moduleroot/spec/acceptance/nodesets/centos-66-x64-pe.yml.erb
  centos6-64mdc (not sure how to get PE in)
moduleroot/spec/acceptance/nodesets/centos-7-x64.yml.erb
  centos7-64
moduleroot/spec/acceptance/nodesets/debian-82-x64.yml.erb
  debian8-64
moduleroot/spec/acceptance/nodesets/fedora-25-x64.yml.erb
  fedora25-64
moduleroot/spec/acceptance/nodesets/fedora-26-x64.yml.erb
  fedora26-64
moduleroot/spec/acceptance/nodesets/fedora-27-x64.yml.erb
  fedora27-64
moduleroot/spec/acceptance/nodesets/ubuntu-server-1404-x64.yml.erb
  ubuntu1404-64
moduleroot/spec/acceptance/nodesets/ubuntu-server-1604-x64.yml.erb
  ubuntu1604-64

It also gives us the more current versions:

  debian9-64
  fedora28-64
  fedora29-64
  ubuntu1804-64

I'm leaving ArchLinux and Windows descriptions for vagrant since I
haven't looked at replacing them. The same goes for the ec2
descriptions.

config_defaults.yml

@@ -88,7 +88,7 @@ Gemfile:
         version: '>= 6'
       - gem: serverspec
       - gem: beaker-hostgenerator
-        version: '>= 1.1.10'
+        version: '>= 1.1.22'
       - gem: beaker-docker
       - gem: beaker-puppet
       - gem: beaker-puppet_install_helper