Home page doesn't show when host is not running

The change made for Proxies in this PR https://github.com/Azure/azure-webjobs-sdk-script/pull/1938 pushed the home page (our fancy landing page) into the function invoke path. That path has the "host running" filter in place, meaning that if the host is in error the landing page isn't shown, and all you see in the browser is a string like "The host is not running".

The landing page should probably show, even if the host isn't running.

Start by reviewing PR 1938 and tracing the function invoke path, especially the "host running" filter described in the issue. Confirm how the landing page is routed when the host is in error. Done means the home page is displayed instead of "The host is not running" when the host is not running.

Written by the indexing model from the issue text.