VMware: Remove some unused variables

Remove unused variables from the following files:

* nova/tests/virt/vmwareapi/test_driver_api.py
* nova/virt/vmwareapi/driver.py
* nova/virt/vmwareapi/volumeops.py

There is no design to the above selection of files: this is simply as
I have encountered them.

Change-Id: I43ee2f71edf5872bfe1b1fe010e83435689501bb
Merge "VMware: Remove some unused variables"