VMware: remove unused class

The Failure class has not been used since it was added
to the code base. This was done in the commit below:-
https://code.launchpad.net/~citrix-openstack/nova/vmware-vsphere-support/+merge/53060

Change-Id: Ib4f0372f847bcbefde27c02b6ce01202482a46c0
Merge "VMware: remove unused class"