Steps to reproduce:

1. All VMs come with a pre-configured zabbix user and zabbix group with specific UID and GID, the same across all datacentre. These settings are managed by system admins.
2. zabbix agent installation is done as root (user zabbix is a sudoer)
3. installation finds an already existing zabbix user and group and leaves them untouched (as expected)
4. agent uninstall

Result:
during uninstall zabbix user gets removed from /etc/passwd and zabbix group is removed from /etc/group. 

Expected:
since zabbix user and group are not created by agent installation, they should not be removed, as this breaks configurations applied by system admins. Besides, when reinstalling the agent, since no zabbix user is defined, a new one will be created, with different id/gid and with nologin making sudo configurations useless and account management will lose track of users on systems.