MAJOR: stream-int: switch from SI_ST_CON to SI_ST_RDY on I/O

MAJOR: stream-int: switch from SI_ST_CON to SI_ST_RDY on I/O

Now whenever an I/O event succeeds during a connection attempt, we
switch the stream-int's state to SI_ST_RDY. This allows si_update()
to update R/W timeouts on the channel and end points to start to
consume outgoing data and to subscribe to lower layers in case of
failure. It also allows chk_rcv() to be performed on the other side
to enable data forwarding and make sure we don't fall into a situation
where no more events happen and nothing moves anymore.