http: use body limit in inspection

When inspecting HTTP bodies there are several limits involved.
In this patch the reaching of the body limit will trigger body
inspection.

Without this, the body would only be inspected when inspection
limits "request-body-minimal-inspect-size" or
"response-body-minimal-inspect-size" were reached. If the body
limit was smaller than this value, the body would only be
inspected at the end of the tx or stream.