Endpoints annotated with AUTH_INTERNAL_ONLY used to be accessible
manually with an internal RPC tool that adds App Engine specific HTTP
headers to a request to make it look like it comes from App Engine
(hence internal). This tool is used by admins to hit such endpoints
during debugging, making them effectively AUTH_INTERNAL_OR_ADMIN.
This RPC tool has never been made available outside Google so the open
source admins do not have such ability. A recent change in the RPC tool
made this hack stop working internally as well. This PR replaces all
all occurances of AUTH_INTERNAL_ONLY with AUTH_INTERNAL_OR_ADMIN and
brings the open source build into feature parity with the internal
version.
Also fixed a few issues the router tests.