Changed upgrade all to only mon.a abd mon.b, added step 4 to upgrade clients before the final workload,
placed both clients on the same node

Signed-off-by: Yuri Weinstein <yuri.weinstein@inktank.com>
Merge pull request #233 from ceph/wip-yuriw-giant

Changed upgrade all to only mon.a abd mon.b, added step 4 to upgrade cli...