Merge "OMX VTS: free graphics buffers at the end of test" am: 7e734892c9 am: 21c5d4e07e am: 5d2c0ccce1

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1552731

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I64b835167bfc22f18406979b77f35462b969c20f