Make http subsystem more chatty on errors

This lets us see various issues in the logs

Change-Id: I634d8b9718de345f82db1af67f157695ae495e6e
Reviewed-on: http://review.couchbase.org/42169
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>