Agent not restarted during (unattended) deb pkg upgrade (systemd)

[d4nys3k]

Wazuh version	Component	Install type	Install method	Platform
4.9.1	Wazuh agent	Agent	Debian packages	all debian/ubuntu versions

During .deb package upgrade in Debian/Ubuntu envinronments with systemd, agent isn't restarted properly.

This is due to bad workflow in preinst/prerm/postinst scripts. See installation workflow in documentation.

At the first, prerm script is called - this stops wazuh-agent. After this, preinst script is called - this script tries to check, if wazuh-agent is running by calling systemctl is-active --quiet wazuh-agent - but at this time unit is already inactive. So ${WAZUH_TMP_DIR}/wazuh.restart file isn't created and code in postinst code doesn't start agent, because ${WAZUH_TMP_DIR}/wazuh.restart doesn't exist.

I think ${WAZUH_TMP_DIR}/wazuh.restart should be created in prerm script to restart agent after upgrade properly.