virsh cleanup with prefix - update inventory file
virsh cleanup with prefix - update inventory file

virsh cleans up only resources that matches the value passed to
'--prefix' when given, but the final task in the cleanup playbook
resets the inventory file to point to a clean one with only the
localhost inside it (like before provisioning).
This patched resests the inventory file only if/when the '--prefix'
isn't given, oterwise, a new task that removes the the relevant nodes
fron the inventory will be executed.

RHOSINFRA-2896

Change-Id: I78c85884cc40f6678ce840a6ddb52628b669fb46

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared