Add systemd mimicking malware files from stage 2 on linux

[huzvanec]

According to the fractureiser-investigation there are two additional files that stage 2 creates in paths /etc/systemd/system/systemd-utility.service and ~/.config/systemd/user/systemd-utility.service that try to mimic some kind of systemd utility.

This pull request simply adds the files to the suspiciousFilesFound list when they exist.