[libvirt] [PATCH 6/7] VMware ESX: Add esxDomainUndefine() based on esxVI_UnregisterVM()

* src/esx/esx_driver.c: add esxDomainUndefine() based on esxVI_UnregisterVM() * src/esx/esx_vi_methods.[ch]: add esxVI_UnregisterVM()