snf-deploy: Use filebased email_backend

Change the email backend from dummy to a filebased one.

snf-deploy/files/etc/synnefo/astakos.conf

@@ -34,7 +34,9 @@ ASTAKOS_PASSWORD_RESET_EMAIL_SUBJECT = 'Password reset on %s' % ASTAKOS_SITENAME
 
 ASTAKOS_COOKIE_DOMAIN = '%DOMAIN%'
 
-EMAIL_BACKEND = 'django.core.mail.backends.dummy.EmailBackend'
+EMAIL_BACKEND = 'django.core.mail.backends.filebased.EmailBackend'
+EMAIL_FILE_PATH = '/var/log/gunicorn/synnefo-mails'
+
 ASTAKOS_SERVICES = {
     'cyclades': {
         'url': 'https://%CYCLADES%/ui/',