misc: let clients use any pool
misc: let clients use any pool

rados.py, for example, creates new pools for each instance.

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