Set the encoding option as utf-8 for logging file. am: 2d7ae10103 am: 15934a1140 am: 11801e989f am: f3d52c86c2 am: 099e3bc1c7

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

Change-Id: I1813a7e0b6940cc99586235a6a17f6f148997916
diff --git a/stress_test.py b/stress_test.py
index d4b2323..1576fbe 100644
--- a/stress_test.py
+++ b/stress_test.py
@@ -230,7 +230,7 @@
 
     if output:
       stress_test_common.MakeDirsIfNeeded(os.path.dirname(output))
-      self.output_fp = open(output, "w")
+      self.output_fp = open(output, "w", encoding="utf-8")
       logging.info("Logging device info to %s", output)
     else:
       self.output_fp = None