Vagrantfile: update and trim as needed
Vagrantfile: update and trim as needed

Some boxes are no longer available, trim those machines from the host
configuration lists.  Each box currently listed has libvirt as a
specified provider, or is compatible with libvirt after a vagrant mutate
has been applied.

wuliming/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,wuliming/pcp