test_ipalib: add test for DNParam class
A single-valued DNParam parameter must not accept multivalues. Add test
checking the behavior for single valued and multivalued DNParam.
Related: https://pagure.io/freeipa/issue/8097
Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>