zabbix-agent doesn't exist anymore since 3.0

'-f' option (foreground) is now in zabbix-agentd

003-change-user-and-foreground.patch fixes pending
issue https://support.zabbix.com/browse/ZBX-10611

you might need to update your config file to add
LogType=system

Signed-off-by: Etienne CHAMPETIER <champetier.etienne@gmail.com>