sysutils/zrepl: Fix rc.d init script on FreeBSD < 11.1

This change removes the daemon syslog feature on FreeBSD < 11.1.
This has little effect to the usefulness of zrepl logging, as the daemon
itself has inbuilt syslog support which is enabled by default in the
sample config file /usr/local/etc/zrepl/zrepl.yml. The only output to
stdout/stderr from zrepl will be if its inbuilt syslog feature is not
working.

PR: 224844
Reported by: Bernhard <bernhard.kneip@postadigitale.de>
MFH: 2018Q2