Import OS-specific vars from task in common role

We stopped being able to do dynamic includes from the playbooks around
Ansible 2.4.0.0 if I recall correctly. Instead we can create a task to
include the variables and make it always run by using the special tag.

For now the Debian and Ubuntu vars files are the same, but I will keep
them separate so that it is more flexible in the future.

vars/Ubuntu.yml

@@ -0,0 +1,10 @@
+---
+
+# sshd service name is `ssh` on Debian/Ubuntu, but it's
+# `sshd` on CentOS
+sshd_service_name: ssh
+
+# provisioning user vars
+provisioning_user: { name: 'provisioning', home: '/home/provisioning' }
+
+# vim: set ts=2 sw=2: