Drop custom ingress controller manifest

[russellb]

This issue is to track the removal of:

https://github.com/openshift-metal3/dev-scripts/blob/master/assets/templates/99_ingress-controller.yaml

This was added to allow ingress to work on 3 masters with no workers. Removing it without any other changes will cause deployment to fail (#699).

[russellb]

This will work when we use the new scheduler config option, schedulableMasters and set it to true. It's set automatically for a 3-node deployment as of openshift/installer#2004.

When that option is set to true, the master nodes have the worker role set on them, which will allow ingress to work on a 3 node cluster.