rgw utils: add function to get data log window configuration
rgw utils: add function to get data log window configuration

Signed-off-by: Josh Durgin <51652c783f70f5b272ebd02f1fd20d3af7a2449f@inktank.com>

ktdreyer/teuthology,tchaikov/teuthology,caibo2014/teuthology,SUSE/teuthology,robbat2/teuthology,ivotron/teuthology,ceph/teuthology,dmick/teuthology,dmick/teuthology,t-miyamae/teuthology,zhouyuan/teuthology,ktdreyer/teuthology,michaelsevilla/teuthology,yghannam/teuthology,michaelsevilla/teuthology,SUSE/teuthology,zhouyuan/teuthology,tchaikov/teuthology,t-miyamae/teuthology,ceph/teuthology,dmick/teuthology,robbat2/teuthology,yghannam/teuthology,SUSE/teuthology,ivotron/teuthology,dreamhost/teuthology,caibo2014/teuthology,dreamhost/teuthology