vmware: default global pbm policy configuration

vmware: default global pbm policy configuration

Adding support for a global pbm policy configuration for the vmdk
driver. Setting the 'pbm_default_policy' in cinder.conf will be
used as the default storage profile name to be used when creating
a volume without associated vmware:storage_profile extra spec.

Also renaming 'vmware-pbm-wsdl' to 'pbm-wsdl-location' to use
nova driver's naming convention.

Implements: blueprint vmdk-storage-policy-volume-type
Change-Id: I7fad167b7be6a479db88fb4d15d07f29afd023b0