Fix syntax of erasure coded pool creation

Signed-off-by: David Zafman <david.zafman@inktank.com>
rados/thrash: Fix workload of cache-agent-big

Create a log of objects and operate on some of them
(Initial object creation counts against total operations specified)
Add limit to 20 minutes

Fixes: 8263

Signed-off-by: David Zafman <david.zafman@inktank.com>
Merge pull request #30 from ceph/wip-8263

Wip 8263