Fixed #6835 -- Use cached FQDN when creating `smtplib.SMTP()` connection to avoid a lengthy

`socket.getfqdn()` call, thanks George Murdocca and PhiR.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7348 bcc190cf-cafb-0310-a4f2-bffc1f526a37