authgraph: add placeholder VTS test am: c8625a8963

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2750487

Change-Id: I17987d6a9371622b1b7b7c38118959f4105f74ae
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>