Update baremetal to work with the latest DIB

Adjust DevStack to the current DIB's naming to kernel/ramdisk.

BM_HOST_CURRENT_KERNEL is removed since the kernel is extracted from
a diskimage with the ramdisk and the host's kernel is not used.

BM_BUILD_DEPLOY_RAMDISK is added to control whether use DIB or not.

If you set BM_BUILD_DEPLOY_RAMDISK=False, you must BM_DEPLOY_KERNEL
and BM_DEPLOY_RAMDISK to point existing deploy kernel/ramdisk.

Fixes bug 1207719

Change-Id: I62af0b1942b07ac12665c0ed3619d64c1cccbe1f
Merge "Update baremetal to work with the latest DIB"