Improve systemd check for Linux scripts

[damgouj]

Environment

1. Linux
2. OpenBAS 1.14.0

Reproducible Steps

Steps to create the smallest reproducible scenario:

1. Launch an installation agent script for Linux on a machine without systemd installed or running

Expected Output

Inform the user if systemd is not installed and if systemd is not running.

Actual Output

Inform the user systemd is not installed but the code checks the running status.