net/scamper: Update to 20161204a

https://mailman.caida.org/pipermail/scamper-announce/2016-December/000009.html
https://mailman.caida.org/pipermail/scamper-announce/2017-June/000010.html

PR: 220216
Submitted by: mjl@luckie.org.nz (maintainer)
Approved by: garga (mentor)
Differential Revision: https://reviews.freebsd.org/D11362