test: Clean up site_login.py a bit.

client/site_tests/login_CryptohomeMounted/login_CryptohomeMounted.py

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import os, utils, time
 from autotest_lib.client.bin import chromeos_constants
 from autotest_lib.client.bin import site_cryptohome, site_login, test
 from autotest_lib.client.common_lib import error
 
 class login_CryptohomeMounted(test.test):
     version = 1
 
     def setup(self):
         site_login.setup_autox(self)
 
     def run_once(self, script='autox_script.json', is_control=False):
-        logged_in = site_login.logged_in()
+        # Make sure that we're logged out initially -- this test is run
+        # multiple times, and we don't want to reuse the previous instance's
+        # session.
+        if site_login.logged_in():
+            site_login.attempt_logout()
 
-        if not logged_in:
-            # Test account information embedded into json file.
-            if not site_login.attempt_login(self, script):
-                raise error.TestFail('Could not login')
+        # Test account information embedded into json file.
+        site_login.attempt_login(self, script)
 
         if (not is_control and
             not site_cryptohome.is_mounted(allow_fail=is_control)):
             raise error.TestFail('CryptohomeIsMounted should return %s' %
                                  (not is_control))
 
-        # If we started logged out, log back out.
-        if not logged_in:
-            if not site_login.attempt_logout():
-                raise error.TestError('Could not log out')
+        site_login.attempt_logout()