rados: reduce boilerplate in TestGetPoolByName using testify
rados: reduce boilerplate in TestGetPoolByName using testify

Testfiy's assert and require libs have helpful functions for
checking values. Use them to reduce a bunch of boilerplate code in the
TestGetPoolByName function.

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

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