Fixes a bug in attaching volumes on Hyper-V

Fixes bug: #1122264

The CIM v2 WMI context needs to be instantiated by the BaseVolumeUtils
class and not passed by the caller of get_iscsi_initiator().

Change-Id: I811b5bd0117b0035c18e5c90169b25a095bc54e9
Merge "Fixes a bug in attaching volumes on Hyper-V"