Based on Coverity scan.
CID: 96660

Extended to also cover other error return places.

Found by: Coverity scan.

	XEN PV environment and load kernels.

	GRUB_DISK_DEVICE_UBOOTDISK_ID.

	for all archives to a separate module. This splits tar from cpio
	as they are very different but keeps cpio, cpio_be, odc and newc
	together since they're very similar.

	platform. Don't try to search for disks already using native drivers.