add missing module to requirements.txt
add missing module to requirements.txt

Signed-off-by: Yehuda Sadeh <48638f9c2a62c4fd20be28d0bdad68f5cd041402@inktank.com>

ceph/radosgw-agent,jdurgin/radosgw-agent,ceph/radosgw-agent,jdurgin/radosgw-agent