Add needed symlink for Fedora deployment ramdisk.

Symlink /usr/lib -> ../lib for Fedora deployment ramdisk.  This
symlink is needed for systemd-udevd.  Otherwise, the network device is
not loaded and initialized when the deployment image is booted.  This
logic was previously contained in
elements/deploy/root.d/50-redhat-prepare-fs, but now that ramdisk
images are built in a chroot, the change needs to be moved so that it
is applied to the ramdisk build.

Change-Id: Icea43230126956ccf5fb8a6a96ca706b75d5c32f
Merge branch 'dev-fedora-ramdisk' of github.com:slagle/diskimage-builder into dev-fedora-ramdisk