Added sequential: clause, so test stop thrashing the mon after it runs that one workload

Signed-off-by: Yuri Weinstein <yuri.weinstein@inktank.com>
Fixed typo

Signed-off-by: Yuri Weinstein <yuri.weinstein@inktank.com>
Merge pull request #109 from ceph/wip_fix_firefly-x

Added sequential: clause, so test stop thrashing the mon after it runs t...