Enable java backend for UpdateEngineStable am: 6c2a6cc7fc

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2889337

Change-Id: Ib5d5a443a40b7a833066a0969c84c6f1887d9724
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>