Changed workloads in 2-workload to run in parallel

@liewegas @tmuthamizhan pls review

Fixes #10233

suite - firefly-x/parallel (giant) only

Test run - http://pulpito.front.sepia.ceph.com/teuthology-2014-12-03_20:34:56-upgrade:firefly-x-giant-distro-basic-vps/

Signed-off-by: Yuri Weinstein <yuri.weinstein@inktank.com>