Fix race in KVM's vm_delete
Fix race in KVM's vm_delete

After powering off a KVM VM, we need to sleep before undefining the VM.

Without the sleep, vm_delete causes an error if the VM in question has
been booted with virt-install (without subsequent reboots).

Change-Id: I40f4e9c6466953c99255271594409e889392c59b

openstack/training-labs,openstack/training-labs,openstack/training-labs