rbd/basic: factor out install + ceph

Signed-off-by: Sage Weil <sage@inktank.com>
rbd: do most tests with a (small) cache pool in front

Signed-off-by: Sage Weil <sage@inktank.com>
rbd/thrash: factor out install + ceph

Signed-off-by: Sage Weil <sage@inktank.com>
Merge pull request #26 from ceph/wip-rbd-cache

test rbd with cache pool

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>