mediapc: Add precondition checks for few tests am: afb068b78d

Original change: https://googleplex-android-review.googlesource.com/c/platform/cts/+/19247169

Change-Id: I932823a993301eb904cd80bd7aa7c0845a42762a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>