kernel-install: Remove existing initramfs if it's older than the kernel
Currently we fail to install a new kernel with "make install" on the second
try, because dracut won't over-write the initramfs without --force. In this
patch, 20-grub.install will remove an existing initramfs if it's newer than the
kernel we're installing.
Signed-off-by: Peter Jones <email@example.com>