Cannot set a field to an instance of a type which doesn't have any properties

[Vipin Balachandran]

oslo.vmware prunes properties which are empty. For example, we need to set VirtualMachineConfigSpec.vmProfile to an instance of VirtualMachineEmptyProfileSpec to remove the policy association. Since VirtualMachineEmptyProfileSpec doesn't have any properties, the suds client prunes it, and hence the reconfig operation becomes NOP.