MEDIUM: http: don't reject anymore message bodies not containing the url param

MEDIUM: http: don't reject anymore message bodies not containing the url param

http_process_request_body() currently expects a request body containing
exactly an expected message body. This was done in order to support load
balancing on a unique POST parameter but the way it's done still suffers
from some limitations. One of them is that there is no guarantee that the
accepted message will contain the appropriate string if it starts with
another parameter. But at the same time it will reject a message when the
buffer is full.

So as a first step, we don't reject anymore message bodies that fill the
buffer.