MAJOR: http: stop using msg->sol outside the parsers

MAJOR: http: stop using msg->sol outside the parsers

This is a left-over from the buffer changes. Msg->sol is always null at the
end of the parsing, so we must not use it anymore to read headers or find
the beginning of a message. As a side effect, the dump of the request in
debug mode is working again because it was relying on msg->sol not being
null.

Maybe it will even be mergeable with another of the message pointers.