qa/workunits/rbd/copy.sh: fix test

I broke this in commit 9d64ac66082bd108ec3c2a74e2e77475b5564eae.

Signed-off-by: Sage Weil <sage@inktank.com>
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
qa/workunits/rbd/copy.sh: skip some tests when tiering is enabled

The rados ls bit doesn't work.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>