Set the Cliff namespace
Set the Cliff namespace

Setting None as namespace was working by chance. Cliff was using it only
in a method we override. But since 2.10, it uses in some other place.

This change put a valid name as cliff namespace.

sileht/python-gnocchiclient,gnocchixyz/python-gnocchiclient,gnocchixyz/python-gnocchiclient