Make ingress hostname configurable

[mikeywuu]

This PR addresses the possibility to add an hostName to the ingress configuration of a given solrcloud instance as described in #667.

The change is quit simple. Unfortunately, the make prepare step failed for me at the fetch-licenses-list step, so the dependency_licenses.csv stays empty in my case.

make: *** [fetch-licenses-list] Error 1

To make the e2e-tests start / work, I also needed to change the RAW_GINKGO command. Not sure if that is an issue only on my machine.

Happy for any feedback!