MAJOR: session: pass applet return traffic through the response analysers

MAJOR: session: pass applet return traffic through the response analysers

Now that applets work like real connections, there is no reason for
them to evade the response analysers. The stats applet emits valid
HTTP responses, it can flow through the HTTP response analyser just
fine. This now allows http-response/rsprep/rspadd rules to be applied
on top of stats. Cookie insertion does nothing since applets are not
servers and thus do not have a cookie. We can imagine compression to be
applied later if the stats output is emitted in chunks and in HTTP/1.1.

A minor visible effect of this change is that there is no more "-1" in
the timers presented in the logs when viewing the stats, all timers are
real.