travis: add ceph nautilus to the test matrix
travis: add ceph nautilus to the test matrix

Add ceph nautilus to the test matrix as well as simplifying the setup
script in the travis yaml file.

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

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