/etc/shadow permissions false positive on Fedora

[marcelhuth]

Hi,
permissions of /etc/shadow are like the ones RedHat uses (000)

796724 ----------. 1 root root 1321 Dec 24 02:40 /etc/shadow

Unfortunately os.redhat? is not true for Fedora systems, so the control fails. I'll work on PR (which should be only checking the os.name)