net-mgmt/librenms: Update to 23.8.2

This port update includes a new cron job which launches the schedule
process. This is distinct from the librenms-service.py daemon recently
introduced and also from the previous poller script.
See /usr/local/etc/cron.d/librenms

This update also installs symlink between /usr/local/bin/lnms and

WWWDIR%%/lnms - this script is used during upgrades and always had
permissions issues when run as non-root. The script attempts to enforce
Linux-specific permissions (e.g. www owned). This symlink satisfies a
validation check the code does.

This commited patches the validation check for lnms. The check assumes
/usr/local/bin is on the path but that is not the case when librenms is
running. Instead, just check that the symlink exists.

files/pkg-message.in - updated to reflect lnms symlink changes

re: https://github.com/librenms/librenms/releases/tag/23.8.2

These releases were skipped over:

* https://github.com/librenms/librenms/releases/tag/23.8.1
* https://github.com/librenms/librenms/releases/tag/23.8.0