Add Vagrant-related packages to ubuntu-cloud packageset

[Daniel Watkins]

Hello,

I've been shepherding a new Vagrant release through proposed migration
over the past couple of weeks (as an ubuntu-cloud uploader), and my life
has been made substantially more difficult by not being able to retry
autopkgtests for its reverse dependencies.

Could we add the following packages to the ubuntu-cloud packageset:

* vagrant-cachier
* vagrant-libvirt
* vagrant-lxc
* vagrant-mutate
* vagrant-sshfs

These are all universe packages that integrate very closely (and
specifically) with Vagrant itself, so I believe they are reasonable
additions to the packageset.


Thanks,

Dan