Secure containers are blocking the mknod, to prevent easy breakout. The problem is we are having a difficult time preventing lvm unit files from firing off and generating some ugly messages about not being allowed to mknod. If you added this flag to your unit file, systemd would not attempt to launch theme when mknod has been removed.
Well, normal unit files can be disabled if they are not intended for use. As for the problem with lvm2-activation-generator, this should be resolved now with bug #961052 - lvm2-2.02.98-9.fc19. *** This bug has been marked as a duplicate of bug 961052 ***
One of the goals here is to make Fedora/RHEL boot on bare metal, in a VM and in a container cleanly without any changes on disk, with the same image, and cleanly. That's why manually disabling services sucks, because then the image that boots in a container won't boot on bare metal anymore.