cleanup-and-unlock.sh: helper to nuke and then unlock a set of nodes

cleanup-and-unlock.sh: helper to nuke and then unlock a set of nodes

I usually do something like

 teuthology-lock --list-targets --owner scheduled_sage@metropolis > /tmp/b
 ./cleanup-and-unlock.sh /tmp/b scheduled_sage@metropolis

It's a huge headache when some of the nodes are down, though.  A better
thing would be if nuke had an --unlock option, and would continue with the
nodes that didn't error out.

But, this is still useful as is.