Set the encoding option as utf-8 for logging file. am: 2d7ae10103 am: 15934a1140 am: 11801e989f am: f3d52c86c2

Original change: https://android-review.googlesource.com/c/platform/tools/test/openhst/+/1427749

Change-Id: I0a182625bed0c450e9325e7336b0840412452981