[MEDIUM] http: restore the original behaviour of option httpclose

[MEDIUM] http: restore the original behaviour of option httpclose

Historically, "option httpclose" has always worked the same way. It
only mangles the "Connection" header in the request and the response
if needed, but does not affect the connection by itself, and ignores
any further data. It is dangerous to change this behaviour without
leaving any other alternative. If an active close is desired, it's
better to make use of "option forceclose" which does exactly what
it intends to do.

So as of now, "option httpclose" will only mangle the headers as
before, and will only affect the connection by itself when combined
with another connection-related option (eg: keepalive or server-close).