Steps to reproduce:

1. Install Zabbix Agent or upgrade it to 4.0.17.
2. Try to start it via "service zabbix-agent start"

Result:
Zabbix Agent doesn't start and it display something like "zabbix-agent stop/pre-start, process 62818"
(PID varies but the rest is constant)
Expected:
Zabbix Agent starts and keeps running.

According to my investigation, the problem is in /etc/init.d/zabbix-agent which is different than in 4.0.16. There are these new lines:

if [ -n "$ZABBIX_AGENT_USER" ]; then
    user_conf="-c $ZABBIX_AGENT_USER"
else
    user_conf=''
fi

This is probably buggy because -c should specify a configuration file and not an user.