Skip lxc tests if no lxc and skip failing vt_test if running osx

Clean up some failing tests:
- If `lxc` hasn't been installed, skip all lxc tests
- One of the `vt_tests` relies on `procfs`, which is not supported in OS X - skipped now mac
This is not cool....
OS X not supporting procfs...

We need to find a workaround...