tests: Remove check for os.set_inheritable
tests: Remove check for os.set_inheritable

This is available on all supported Python versions.

Change-Id: I76a696e56e04ec47b107af8e169c04138cf45fbb
Signed-off-by: Stephen Finucane <492121341a95b3c3aab646bed44634f739dd019b@redhat.com>

openstack/glance,openstack/glance,openstack/glance