task/pexec: More fixes for all case, exec on hosts
task/pexec: More fixes for all case, exec on hosts

We don't want to do an exec per role, but per-host.  We
were already doing an exec per host, but the names were confusing.
This fixes the names up and removes the role parameters.

Signed-off-by: Sam Lang <70ab3b98ad075c66e7d3501cb42b80a7e41da316@inktank.com>

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