test: Clean up site_login.py a bit.

client/site_tests/login_CryptohomeUnmounted/login_CryptohomeUnmounted.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, time
 from autotest_lib.client.bin import site_cryptohome, site_login, test
 from autotest_lib.client.common_lib import error
 
 class login_CryptohomeUnmounted(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()
 
         # Require that the cryptohome is mounted before testing that
         # logging out will unmount it.  This requires logging in.
         if not logged_in:
-            if not site_login.attempt_login(self, script):
-                raise error.TestError('Could not login')
+            site_login.attempt_login(self, script)
 
         if not site_cryptohome.is_mounted(allow_fail = is_control):
             raise error.TestFail('Expected cryptohome to be mounted')
 
-        if not site_login.attempt_logout():
-            raise error.TestError('Could not logout')
+        site_login.attempt_logout()
 
         # allow the command to fail, so we can handle the error here
         if site_cryptohome.is_mounted(allow_fail = True):
             raise error.TestFail('Expected cryptohome NOT to be mounted')
 
         # If we started logged in, reset the state.
         if logged_in:
-            if not site_login.attempt_login(self, script):
-                raise error.TestError('Could not login')
+            site_login.attempt_login(self, script)