Switch mkenvimage to new one supported by cf team am: 3b031a6b4d

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Virtualization/+/2055367

Change-Id: Ie143844ccc2191264b34ed93600dff0c24ea1e80
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>