adb: win32: fix unittest exit code parsing

adb on Windows uses \r\n line-endings, so take that into account when
parsing output for the exit code.

Change-Id: I6a3d7c5ca455b0f0f7dae174866857e0aeee9926
Signed-off-by: Spencer Low <CompareAndSwap@gmail.com>
diff --git a/device.py b/device.py
index bc1364b..5b33ff2 100644
--- a/device.py
+++ b/device.py
@@ -112,7 +112,8 @@
     _RETURN_CODE_PROBE_STRING = 'echo "{0}$?"'.format(_RETURN_CODE_DELIMITER)
 
     # Maximum search distance from the output end to find the delimiter.
-    _RETURN_CODE_SEARCH_LENGTH = len('{0}255\n'.format(_RETURN_CODE_DELIMITER))
+    # adb on Windows returns \r\n even if adbd returns \n.
+    _RETURN_CODE_SEARCH_LENGTH = len('{0}255\r\n'.format(_RETURN_CODE_DELIMITER))
 
     def __init__(self, serial, product=None):
         self.serial = serial