Update the devstack script to point to the correct PowerMax drivers
and to leverage the new PowerMax tags in cinder.conf merged in
https://review.openstack.org/#/c/620659.
Will change the name of the git repo at a later date.
Change-Id: I0139e1ffd04ac7eb33021cd276e5b27379da79d0
The use of xml files for configuration is deprecated. This fix switches
configuration options to cinder.conf
Change-Id: I0bcd47f0ff32cf4031d5d0390f1a899516e66cb9
blueprint: backend-xml-deprecation