Fix race in listening to session stop signal.

BUG=chromium:344173
TEST=trybot

Change-Id: I8e915236a4aee79f4dbd8afe78597980b4617e3b
Reviewed-on: https://chromium-review.googlesource.com/186847
Reviewed-by: Chris Masone <cmasone@chromium.org>
Commit-Queue: Achuith Bhandarkar <achuith@chromium.org>
Tested-by: Achuith Bhandarkar <achuith@chromium.org>
diff --git a/client/site_tests/login_LoginSuccess/login_LoginSuccess.py b/client/site_tests/login_LoginSuccess/login_LoginSuccess.py
index 2ed6031..2b6cd6c 100644
--- a/client/site_tests/login_LoginSuccess/login_LoginSuccess.py
+++ b/client/site_tests/login_LoginSuccess/login_LoginSuccess.py
@@ -35,6 +35,8 @@
             # To enable use as a 'helper test'.
             self.job.set_state('client_success', True)
 
-        self._listener.listen_for_session_state_change('stopped')
+            # Start listening to stop signal before logging out.
+            self._listener.listen_for_session_state_change('stopped')
+
         self._listener.wait_for_signals(desc='Session stopped.',
                                         timeout=self._SESSION_STOP_TIMEOUT)