nuke: Power off FOG machines instead of reimaging
nuke: Power off FOG machines instead of reimaging

Now that FOG is in master, we don't have to reimage on nuke. Let's shut
them down - the next job will bring them up again during the reimage
process.

Signed-off-by: Zack Cerza <d7cdf09fc0f0426e98c9978ee42da5d61fa54986@redhat.com>

ceph/teuthology,ktdreyer/teuthology,ceph/teuthology,dmick/teuthology,ktdreyer/teuthology,SUSE/teuthology,dmick/teuthology,dmick/teuthology,SUSE/teuthology,SUSE/teuthology