Pertaining to RedHat's Bug 1043212 is an issue experienced back in December about Fedora 20 with a fundamental issue of /var/run/nologin being incorrectly generated.
As the user explained and acknowledged by the bug comments, "The above bug, which is crosslinked with other bugs, describes a problem with gnome-shell and systemd that cause people to loose control over their system once the shielding of gnome-shell happens (automatic shield or forced with super+l). People can not log into their machines anymore or even switch to console to logout properly. Another user reported that because of this, you can go into hibernation and once you come out of hibernation (once above issue happens) that you don't need any password to bypass gnome shield. You gain access to the machine instantly and take over its control."