project-lakitu: change default mnt pt for ephemeral on azure

Based on cloud-init default cfg, ephemeral0 is mounted
to /mnt which clobbers /mnt/stateful_partition,
so changing the /mnt/empty.

As per crbug.com/934513, /mnt/empty was added for crosvm,
which is not used on cos on azure. So

BUG=b/177096550
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I6609f4cbe1c9ea0b65b60bd1ccec492fe47616d1
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/11290
Reviewed-by: Roy Yang <royyang@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
2 files changed