[master] Better handling output of `systemctl --version`

[vzhestkov]

What does this PR do?

In some cases calling systemctl --version with salt.grains.core._systemd could return unexpected output what could cause IndexError exception preventing minion service from running.

What issues does this PR fix or reference?

Tracks https://github.com/SUSE/spacewalk/issues/25122

Previous Behavior

IndexError exception on starting minions service caused by unexpected response of systemctl --version

New Behavior

Normal minion start with just error message in the log about unexpected output.

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• [ ] Docs
• [ ] Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• [ ] Tests written/updated

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