Fix Redmine 13444 - Add zabbix agent+proxy package log files owner and mode (fixes log rotations)

[cyrilchristin]

Redmine Issue 13444

Fixes the permissions issue for the zabbix agent and proxy packages log files that occurs upon log rotation.

The log rotation would incorrectly set the user/group to the (default) root:wheel and set (default) permissions 600.
This would prevent the zabbix agent and proxy from writing to their log files until their services were restarted.

This issue would appear in the logs Status > System Logs > Packages > Zabbix Agent/Proxy as follows:

# Zabbix Agent Log Entries
zabbix_agentd [75082]: failed to open log file: [13] Permission denied
zabbix_agentd [75082]: failed to open log file: [13] Permission denied
zabbix_agentd [75082]: failed to open log file: [13] Permission denied
zabbix_agentd [75082]: failed to open log file: [13] Permission denied
zabbix_agentd [75082]: failed to open log file: [13] Permission denied
   ### lines above repeat ###
Apr 30 04:22:00 pfSense-Tests newsyslog[75419]: logfile turned over due to size>500K

# Zabbix Proxy Log Entries
zabbix_proxy [66641]: failed to open log file: [13] Permission denied
zabbix_proxy [65053]: failed to open log file: [13] Permission denied
zabbix_proxy [63805]: failed to open log file: [13] Permission denied
zabbix_proxy [64771]: failed to open log file: [13] Permission denied
zabbix_proxy [65545]: failed to open log file: [13] Permission denied
   ### lines above repeat ###
Apr 30 03:49:00 pfSense-Tests newsyslog[20325]: logfile turned over due to size>500K`

[jim-p]

As a part of this pull request, you must increase PORTVERSION or add a PORTREVISION line in the package Makefile. Without this version increase, the package will not be rebuilt to include the new change.

See https://docs.netgate.com/pfsense/en/latest/references/developer-style-guide.html#ports-packages-specific-rules