ssh_statemach_act() is now modified to loop over the switch() to perform as

ssh_statemach_act() is now modified to loop over the switch() to perform as
much as possible in one go, as long as it doesn't block and hasn't reached the
end of the state machine.
This avoids spurious -1 returns from curl_multi_fdset() simply because
previously it would return from this function without anything in EWOUDLBLOCK
and thus basically it wasn't actually waiting for anything!!