net-mgmt/check_mk_agent: Update to 1.5.0p12

Changelog:
https://mathias-kettner.com/check_mk-werks.php?edition_id=raw&branch=1.5.0&version=1.5.0p12&HTML=yes

Reviewed by: mat
Approved by: mat (mentor)
Sponsored by: BALLY WULFF Games & Entertainment GmbH
Differential Revision: https://reviews.freebsd.org/D19292