This commit adds support for uefi systems in the image
extension so that grub can be installed onto efi system
partition for uefi machines.
Implements: blueprint local-boot-support-with-partition-images
Change-Id: I8fbb4b2ebdff991d41c7b618a4d654af26311a56
Initially this extension supports installing a bootloader so the user
image can boot from the local disk.
Change-Id: Ia588aafc240b55119c02f1254addc0cf796f88c5