Prevent parse errors after failing to deliver a client request with body

Prevent parse errors after failing to deliver a client request with body

For now we err on the safe side and simply throw all the following
requests under the bus, even if no client body has been buffered.
A compliant client will repeat the dropped requests on an untainted
connection.

The proper fix is to discard the no longer needed client body
in the buffer (if there is one) and to continue parsing the
bytes that follow. This is less trivial and will have to wait
until the next release.

Reported by Basil Hussain.