Add teuthology-kill

Currently implements killing suites-runs.

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Rewrite portions of teuthology.kill

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Merge pull request #139 from ceph/wip-6342

Add teuthology-kill