net-mgmt/cacti: Update to 1.1.13 (Fixes security vulnerability)

Changes: https://www.cacti.net/release_notes.php?version=1.1.13

PR: 220742
Submitted by: Daniel Austin <freebsd-ports@dan.me.uk> (maintainer)
Approved by: garga (mentor, implicit)
MFH: 2017Q3