Ceph » rgw

Failures are all (except for some intermittent) with EC backend. I guess it's related to the fix to #8311. Beforehand we ended up creating a new extra-data pool with empty name, now we revert to using the data pool name, which can't realy be used in the case of EC backend. I think the best (and easiest) solution here is to have default non-empty pool name for the extra-data pool.