PowerMax config options have changed since Newton.
Updating them to the latest and support both iSCSI
and FC drivers.
CinderPowermaxBackend is also enhanceded to support
multiple backends. CinderPowermaxBackendName supports a
list of backend names and a new CinderPowermaxMultiConfig
parameter provides a way to specify parameter values for
each backend. For example see file
environments/cinder-dellemc-powermax-config.yaml
Depends-On: https://review.opendev.org/#/c/712184
Change-Id: I4429ed2d45661ea82ae38a7050abb2b229953c9c