pam_login_access: Fix negative entry matching logic

PR: 252194
Approved by: re (implicit, so)
Approved by: so
Security: CVE-2020-25580
Security: FreeBSD-SA-21:03.pam_login_access

(cherry picked from commit 6ab923cbca8759503a08683a5978b9ebf5efd607)
(cherry picked from commit 8cf559d6b9b4782bf67eb868ea480f47fc8c64a4)