Provide initrd kernel modules to the real root, if the real root hasn't any

[haraldh]

"bind-mount" kernel drivers in real root for the e.g. the rescue image, if the real root does not have any kernel modules for this kernel

see https://bugzilla.redhat.com/show_bug.cgi?id=1046510

This can be accomplished by adding kmod config files in /run pointing to the provided initrd kernel modules directory.

[LaszloGombos]

Similar feature in another initramfs generator - https://bazaar.launchpad.net/~smoser/ubuntu/xenial/cloud-initramfs-tools/pkg/view/head:/copymods/scripts/init-bottom/copymods#L63