Sanitize default names, limit to 63 chars

I discovered today that CentOS 7 apparently shipped with [this bug](https://bugzilla.mindrot.org/show_bug.cgi?id=2239). Creating a CentOS 7 server in DigitalOcean with a name > 63 characters results in a server with broken SSH access (port 22 not even open).

This change ports over [all](https://github.com/test-kitchen/kitchen-openstack/pull/20) [the](https://github.com/test-kitchen/kitchen-openstack/pull/49) [changes](https://github.com/test-kitchen/kitchen-openstack/pull/50) that were made to kitchen-openstack to get around naming issues. Limits names to <= 63 characters and strips out potentially-problematic punctuation.