Add Dwellers as lxc provider
Summary:
Dwellers is a server for Docker / LXC / OpenShift capabilities.
As such, it's the host for the lxc mailserver container.
Reference: https://docs.saltstack.com/en/latest/topics/cloud/lxc.html
Ref T1196
Test Plan: Provide a lxc container
Reviewers: dereckson
Reviewed By: dereckson
Maniphest Tasks: T1196
Differential Revision: https://devcentral.nasqueron.org/D978