pf: Free pf_rule_items when state is not created

This addresses the issues of pf_rule_times leaking in case of stateless
rules and in case of state creation failures, like hitting the state
limit.

Reviewed by: kp
MFC after: 1 week
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D42169

(cherry picked from commit 4d19eceaefb7106d761bc9504bb0da737ae0d674)