Title: #1920: ui_tests: improve "field_validation" method
Often when trying to check e.g. required field we pass the method another element as
parent in order to narrow down a scope for validation. This way we can just pass
"field" name to make the process easier.
To pull the PR as Git branch:
git remote add ghfreeipa https://github.com/freeipa/freeipa
git fetch ghfreeipa pull/1920/head:pr1920
git checkout pr1920