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

Merge "Revert "transcoding: use background io priority"" into sc-dev am: 5363fb4b am: ca31057e am: 4a37cb3b

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

Change-Id: I8cfbefe29b6d0af60d3f4a8a24fc78c6207043e4