Rework route_input() and rtm_sendup(). While we perform foreach loop

Rework route_input() and rtm_sendup(). While we perform foreach loop
in route_input() we drop solock() after we checked socket state. We
pass mbuf(9) to this socket at next loops, while it referenced as
`last'. Socket's state could be changed by concurrent thread while
it's not locked.

Since we perform socket's checks and output in same iteration, the
logic which prevents mbuf(9) chain copy for the last socket in list
was removed.

ok bluhm@ claudio@