Cleanup WSGI config for keystone on stop

Ensure that the VHOST and the scripts used to enable keystone under
mod_wsgi are properly cleaned up.

Change-Id: I76a748b0fd5f1a5182d10e425202857c5621e25a
Merge "Cleanup WSGI config for keystone on stop"
Merge branch 'master' of github.com:openstack-dev/devstack