Merge "Revert "transcoding: use background io priority"" into sc-dev am:...

Merge "Revert "transcoding: use background io priority"" into sc-dev am: 5363fb4b am: 9e3fd814 am: c62c174c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/14427294

Change-Id: I4c64f1716b057f4dc01a94f1a97de8c28649a7a4