Automatic merge from submit-queue
Move nginx ingress e2e to slow
Normal GCE L7 e2e takes ~15m and runs in a feature private suite. This e2e ensure that the api isn't broken, by creating an nginx controller. I plan to write a really slimmed down version for presubmit, but I need to shave off a minute to get it below 5m.
Fixes https://github.com/kubernetes/kubernetes/issues/23416