Steps to reproduce:

1. fgrep User= /etc/zabbix/zabbix_agentd.conf | egrep -v "^#"
   User=root
2. Update Zabbix agent from 4.0.14 to 40.15 (from repository)
3. ps aux | fgrep zabbix_agentd
6. ...

Result:
zabbix 12042 0.0 0.0 77696 1392 ? S nov26 0:00 /usr/sbin/zabbix_agentd -c /etc/zabbix/zabbix_agentd.conf
zabbix 12043 0.0 0.0 77696 2032 ? S nov26 0:20 /usr/sbin/zabbix_agentd: collector [idle 1 sec]
zabbix 12044 0.0 0.0 81932 2568 ? S nov26 0:20 /usr/sbin/zabbix_agentd: listener #1 [waiting for connection]
zabbix 12045 0.0 0.0 81932 2568 ? S nov26 0:19 /usr/sbin/zabbix_agentd: listener #2 [waiting for connection]
zabbix 12046 0.0 0.0 81932 2600 ? S nov26 0:19 /usr/sbin/zabbix_agentd: listener #3 [waiting for connection]
zabbix 12047 0.0 0.0 81944 2192 ? S nov26 0:03 /usr/sbin/zabbix_agentd: active checks #1 [idle 1 sec]
Expected:
root 12042 0.0 0.0 77696 1392 ? S nov26 0:00 /usr/sbin/zabbix_agentd -c /etc/zabbix/zabbix_agentd.conf
root 12043 0.0 0.0 77696 2032 ? S nov26 0:20 /usr/sbin/zabbix_agentd: collector [idle 1 sec]
root 12044 0.0 0.0 81932 2568 ? S nov26 0:20 /usr/sbin/zabbix_agentd: listener #1 [waiting for connection]
root 12045 0.0 0.0 81932 2568 ? S nov26 0:19 /usr/sbin/zabbix_agentd: listener #2 [waiting for connection]
root 12046 0.0 0.0 81932 2600 ? S nov26 0:19 /usr/sbin/zabbix_agentd: listener #3 [waiting for connection]
root 12047 0.0 0.0 81944 2192 ? S nov26 0:03 /usr/sbin/zabbix_agentd: active checks #1 [idle 1 sec]

Background:

In CentOS 6 and Debian 8 servers I am running Zabbix agent as root because "zabbix" user can not see all user processes and "proc.num" does not work. I tried "hidepid" in /proc mounting but does not work neither.