tests: fix failing HTTPS connection
    
    Recent certificate refactoring probably unclogged some failure
    in handling certificates which causes test_changepw to correctly
    fail since it is trying to connect using an HTTPS connection
    without the CA certificate. This patch adds the CA cert to the
    connection.
    
    https://pagure.io/freeipa/issue/4985
    
    Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>