upgrade/firefly: upgrade client host before doing final workloads

This triggered an error on older because s3tests triggers a but in the
original radosgw, but we may as well do it for the newer/ ones too.

Fixes: #9866
Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #209 from ceph/wip-9866

upgrade client node before finish