Rework event stream http route parsing

It turns out that, even though it only needs a host, the event stream http routing requires passing an http url. But the config parsing we use ends up parsing foo.http://example.org: bar as foo.http = //example.org: bar, so we can't use that. Adjust to accept a k=v pair as the argument and ignore the initial key.

This was retained as a map, even though we ignore the key, is because it is much more convenient to configure maps over lists in helm.

Change-Id: I09ae64860133623adacbc60236975e7860c54bae