ipatests: test_epn: add test_EPN_connection_refused
Add a test for EPN behavior when the configured SMTP does not
accept connections.
Fixes: https://pagure.io/freeipa/issue/8445
Signed-off-by: François Cami <fcami@redhat.com>
Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>