MINOR: http-fetch: Rely on addresses at stream level in HTTP sample fetches

MINOR: http-fetch: Rely on addresses at stream level in HTTP sample fetches

Client source and destination addresses at stream level are now used to
compute base32+src and url32+src hashes. For now, stream-interface addresses
are never set. So, thanks to the fallback mechanism, no changes are expected
with this patch. But its purpose is to rely on addresses at the stream
level, when set, instead of those at the connection level.