[MEDIUM] session: initialize server-side timeouts after connect()

[MEDIUM] session: initialize server-side timeouts after connect()

It was particularly embarrassing that the server timeout was assigned
to buffers during an accept() just to be potentially changed later in
case of a use_backend rule. The frontend side has nothing to do with
server timeouts.

Now we initialize them right after the connect() succeeds. Later this
should change for a unique stream-interface timeout setting only.