pf_map_addr() can fail and in this case we should drop the packet,
otherwise bad consequences including a routing loop can occur.

Move pf_set_rt_ifp() earlier in state creation sequence and
inline it, cutting some extra code.

PR:		183997
Submitted by:	Kajetan Staszkiewicz <vegeta tuxpowered.net>
Sponsored by:	InnoGames GmbH
Do not lookup source node twice when pf_map_addr() is used.

PR:		184003
Submitted by:	Kajetan Staszkiewicz <vegeta tuxpowered.net>
Sponsored by:	InnoGames GmbH