Pass validations errors for HTTP requests

Change-Id: Ieb9372fb9b8acafe045431ccda9c6ee1ccb80f04
Reviewed-on: http://review.couchbase.org/26711
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>