ipaclient/vars/default.yml: Use python3-libselinux instead of libselinux-python

The python3 bindings should be required and not the python2 bindings as a
default.

roles/ipaclient/vars/default.yml

 # defaults file for ipaclient
 # vars/default.yml
-ipaclient_packages: [ "ipa-client", "libselinux-python" ]
+ipaclient_packages: [ "ipa-client", "python3-libselinux" ]
 #ansible_python_interpreter: '/usr/bin/python3'