net-mgmt/cacti: Update to 1.1.28

PR: 223756
Submitted by: freebsd-ports@dan.me.uk (maintainer)
Approved by: olivier (mentor)
MFH: 2017Q4
Security: CVE-2017-16641
Security: CVE-2017-16660
Security: CVE-2017-16661
Security: CVE-2017-16785
Differential Revision: https://reviews.freebsd.org/D13175