rbd: replace tests conn setup boilerplate with func
rbd: replace tests conn setup boilerplate with func

In the rbd tests the setup of the rados connection was essentially copy
and paste with very little proper error checking.
This change adds a common setup function that checks all error
conditions as well as prevents the tests from blocking forever if
something is wrong with the ability of the tests to connect.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph