Some middlewares (notably staticweb) use the absence of a REMOTE_USER to
determine that a request was unauthenticated and as a result should be
handled differently. This could cause problems for S3 requests that
were authenticated via s3api's custom auth logic, including
* server errors when a container listing request gets handled by
staticweb or
* losing storage policy information because staticweb copied the request
environment.
Change-Id: Idf29c6866fec7b413c4369dce13c4788666c0934
Closes-Bug: #1833287
Related-Change: I5fe5ab31d6b2d9f7b6ecb3bfa246433a78e54808
d022781bc6