Fix trigger in Zabbix 4.0 LTS, add support to systemd 219 (CentOS 7)

[valerio-bozzolan]

Changes included in this pull request (batteries included):

• https://github.com/MogiePete/zabbix-systemd-service-monitoring/pull/37/commits/65ac4fab00cd12b1bf98ab6ce1c595476e2db934 - fix the "status" trigger in Zabbix 4.0 LTS
• https://github.com/MogiePete/zabbix-systemd-service-monitoring/pull/37/commits/f6844c4799d5b41efcd7c895b699135b3dc83637 - add support to systemd 219 (welcome again CentOS 7)
• https://github.com/MogiePete/zabbix-systemd-service-monitoring/pull/37/commits/2263deb6806d298cb002980de4aa1d433da8da55 - rename 2 files so that are visible from GitHub web (before this change they are truncated)

I've splitted my pull request in multiple very small commits to help maintainer in reviewing.

NOTE: I've NOT modified the template of version 5 or the scripts for version 5. If you want, you can test my scripts also in a recent version and I think it will work, so you can adopt my "old" scripts for both versions. But, to be more friendly, I have not taken this decision for you, so I'm keeping both.

Thank you :)

[valerio-bozzolan]

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