DevStack: Fix cleaning up nodes with NVRAM (UEFI)
DevStack: Fix cleaning up nodes with NVRAM (UEFI)

This patch is fixing the cleanup_nodes.sh script to take in account
undefining nodes with NVRAM set (UEFI mode). The --nvram option is now
being passed to the "virsh undefine" command, this will undefine nodes
with (and without) NVRAM set.

Change-Id: Idbc2d0d1765cad969e68544109bd44963cadc06c
Closes-Bug: #1659335

SauloAislan/ironic,SauloAislan/ironic,openstack/ironic,NaohiroTamura/ironic,pshchelo/ironic,NaohiroTamura/ironic,pshchelo/ironic,openstack/ironic