VMware: Fix initialization of datastore selector

The WSDL URL of storage policy service is determined and a session is
created using it in do_setup(). This session is later used to initialize
the datastore selector property (ds_sel), which uses the session for all
storage policy related API calls.

After commit a8fa3ceb1e72bac2ab67f569a2ca009f995f59fd (Integrate
OSprofiler and Cinder), the properties defined in vmdk module are called
before do_setup(). As a result, the ds_sel (datastore selector) property
is initialized with a session instance containing a 'None' PBM (storage
policy service) WSDL URL. This results in failures of all storage policy
related APIs invoked using datastore selector. This patch fixes the
problem by re-initializing the property in do_setup().

Change-Id: Ibdf8b23f9e215000cf9053b81d374066fabd6851
Closes-Bug: #1380675
Merge "VMware: Fix initialization of datastore selector"