webui-ci: fix table widget add
add_table_record call used old selector for add button which
caused 3 fails in CI:
- ERROR: Test automember rebuild membership feature for hosts
- ERROR: Test automember rebuild membership feature for users
- ERROR: Basic CRUD: dns
related to:
https://fedorahosted.org/freeipa/ticket/4258
Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>