rados: Add hit_set_list missing from possible op weights

For the future help keep in sync with test/osd/TestRados.cc by listing
in order of op_types in that code.

Signed-off-by: David Zafman <david.zafman@inktank.com>
Merge pull request #269 from ceph/wip-radosfix

rados: Add hit_set_list missing from possible op weights