[Devil] Run devil real device tests on android devices when available.

devil/devil/android/device_utils_devicetest.py

Index: devil/devil/android/device_utils_devicetest.py
diff --git a/devil/devil/android/device_utils_devicetest.py b/devil/devil/android/device_utils_devicetest.py
index 9a50373823eac327132ed0fa15ea425b9464ce9d..33c1fb934307dd9aa80ea901d36a7b5b4892c481 100755
--- a/devil/devil/android/device_utils_devicetest.py
+++ b/devil/devil/android/device_utils_devicetest.py
@@ -9,9 +9,14 @@ The test will invoke real devices
 """
 
 import os
+import sys
 import tempfile
 import unittest
 
+if __name__ == '__main__':
+  sys.path.append(
+      os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..', )))
+
 from devil.android import device_utils
 from devil.android.sdk import adb_wrapper
 from devil.utils import cmd_helper