1. The current origin multicast tests only run under openshift-sdn; they should be run in e2e-ovn tests as well. (The InOpenShiftSDNContext/InOVNKubernetesContext stuff will need to be updated to have an "if either sdn or ovn" version as well.)

2. The current test uses omping and requires its own special test image (https://github.com/openshift/test-multicast), which has multiple problems (based on CentOS 7, only available from docker.io, only available on x86_64). Rather than bothering to fix the existing image, we should just port the test case to use iperf from the agnhost image, like the upstream ovn-kubernetes multicast test does.

3. (Once we no longer depend on the test-multicast image we should archive that git module.)

(Note that part 2 blocks some OCP multi-arch work.)

Note related to https://issues.redhat.com/browse/SDN-545