MFC r335569:

pf: Support "return" statements in passing rules when they fail.

Normally pf rules are expected to do one of two things: pass the traffic or
block it. Blocking can be silent - "drop", or loud - "return", "return-rst",
"return-icmp". Yet there is a 3rd category of traffic passing through pf:
Packets matching a "pass" rule but when applying the rule fails. This happens
when redirection table is empty or when src node or state creation fails. Such
rules always fail silently without notifying the sender.

Allow users to configure this behaviour too, so that pf returns an error packet
in these cases.

PR: 226850
Submitted by: Kajetan Staszkiewicz <vegeta tuxpowered.net>
Sponsored by: InnoGames GmbH