pflog: pass the action to pflog directly

If a packet is malformed, it is dropped by pf(4). The rule referenced
in pflog(4) is the default rule. As the default rule is a pass
rule, tcpdump printed "pass" although the packet was actually
dropped. Use the actual action, rather than the rule's action, or an
attempt at guessing the correct action.

Inspired by OpenBSD's 'pflog(4) logs packet dropped by default rule with block.' commit.

Sponsored by: Rubicon Communications, LLC ("Netgate")