rbd: default to all:
rbd: default to all:

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