Add Linux Mint detection

* Linux Mint is a popular distribution based on Ubuntu
* When creating a VM based on Linux Mint, it cannot detect
that it is based on Ubuntu and it is detected as just linux
and configure_networks fails
* https://github.com/mitchellh/vagrant/issues/3647
Merge pull request #3648 from chrisvire/fix/master/add_mint_guest

Add Linux Mint detection