Fix TEMPEST_AUTH_VERSION comparision condition for identity v2
Fix TEMPEST_AUTH_VERSION comparision condition for identity v2

TEMPEST_AUTH_VERSION should be 'v3' or 'v2' not 'v2.0'.
To disable the identity v2 admin tests TEMPEST_AUTH_VERSION is
being compared with 'v2.0' which is incorrect.

Change-Id: I5f7e3bcf733edbbee06016bcad4845dda552815e

nawawi/openstack,openstack-dev/devstack,dtroyer/devstack,group-policy/devstack,noironetworks/devstack,openstack-dev/devstack,group-policy/devstack,noironetworks/devstack,nawawi/openstack,dtroyer/devstack