[autotest] Ensure that we clear /tmp/uptime-login-prompt-ready before starting a new test

client/bin/site_login.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 errno, logging, os, re, utils, signal, subprocess, time
 from autotest_lib.client.bin import chromeos_constants, site_cryptohome
 from autotest_lib.client.bin import site_utils, test
 from autotest_lib.client.common_lib import error, log_watcher, site_ui
 
 _DEFAULT_TIMEOUT = 30
@@ skipping 273 matching lines @@
 
     Args:
         timeout: float number of seconds to wait
 
     Raises:
         UnexpectedCondition: called while already logged in
         TimeoutError: chrome didn't start before timeout
     """
     if logged_in():
         raise UnexpectedCondition('Already logged in')
+    wait_for_browser()
+    wait_for_login_prompt()
     try:
       os.unlink(chromeos_constants.LOGIN_PROMPT_READY_MAGIC_FILE)
     except OSError, e:
       if e.errno != errno.ENOENT:
         raise e
-    wait_for_browser()
     nuke_process_by_name(chromeos_constants.BROWSER, with_prejudice=True)
     wait_for_browser()
     wait_for_login_prompt()