pf: stop resolving hosts as dns that use ":" modifier

When the interface does not exist avoid passing host with special pf
modifiers to DNS resolution as they come up empty anyway.

Reviewed by: kp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D35429

(cherry picked from commit 28b64169eace3477abbd50c18163d37c45cf273a)