python-lxc: use setuptools instead of distutils

python-lxc: use setuptools instead of distutils

setuptools is recommended by Python Packaging Guide
https://python-packaging-user-guide.readthedocs.io/en/latest/current/

It contains some useful extensions like 'develop' command. Also it
is required for building wheels AFAIK.

The only downside is an extra build-time dependency. setuptools are
packaged in both Debian and Ubuntu (python3-setuptools), as well as
other major distros, so it shouldn't be an issue, I think.

Signed-off-by: Aleksandr Mezin <mezin.alexander@gmail.com>