Bugfix: Log out from Administrator tab raises popup errors

This bug turns out to be caused by we change the login format from
login-window to tranditional login format. After the logout, we can no
longer and there is no need to update the pages and popup a login
window. Now we redirect to login.html after logout.

Signed-off-by: Wen Wang <wenwang@linux.vnet.ibm.com>