vmware: PBM wsdl file configuration

vmware: PBM wsdl file configuration

Currently the PBM wsdl files have to be downloaded to the local file
system and needs to be configured in 'pbm_wsdl_location'. If it is
manually configured then PBM feature is enabled.

This patch does away with the manual configuration of
'pbm_wsdl_location'. PBM wsdl files are now shipped with the driver.
VC version is fetched from the backend server and the corresponding
wsdl file is used. If the backend is a VC version that is less than
5.5 then PBM feature is turned off.

Implements: blueprint vmdk-storage-policy-volume-type
Change-Id: I559006b532fa39aab6d54cb0b21d5f7afba62af3