E2E only pulls from MCR

Make sure E2E relies only on images pulled from MCR. These images were found after a quick search.

- [ ] sturrent/dns-loop
- [ ] docker.io/kennethreitz/httpbin
- [ ] registry.k8s.io/e2e-test-images/nginx:1.14-1
- [ ] ubuntu:18.04
- [ ] oeciteam/sgx-test:1.0
