C2 VTS: Enable AdaptiveBitrateTest only for CDD mandated encoders am: 15ccfa68a8 am: e5ac6fbdaa am: aee1acb55a am: ae21a14c00

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/15898098

Change-Id: I0289fa96897b852df09c10d166d75fbf9df7aa3a