Drive-by: Tighten domain_remap assertions on listings, which required
that we fix proxy pipeline placement. Add a note about it to the sample
config.
Change-Id: I41835148051294088a2c0fb4ed4e7a7b61273e5f
... so we can use storage_url for actual, complete URLs.
Also, expose storage_scheme for easier comparisons.
Change-Id: Iffcfc327bc674681ac51fe75c1d9911fa3a60d54