Fix the AUTH URL v2 to v3 conversion
Fix the AUTH URL v2 to v3 conversion

The current approach to transform the v2 auth url into a v3 one
only works if there is no trailing slash.
Using dirname handles both cases.

Change-Id: Ib3d46ece28b3ee7929da865ac2fa5426046abb05

radez/tripleo-image-elements,rdo-management/tripleo-image-elements,openstack/tripleo-image-elements,openstack/tripleo-image-elements,rdo-management/tripleo-image-elements,radez/tripleo-image-elements