ipahbacrule.py

FreeIPA provides a default hbacsvcgroup named "Sudo", with capital 'S',
that is different from every other hbacsvcgroup, which are all
represented by lower case letters.

As data from IPA API was not modified, this causes an idempotence error
when using different capitalization with the 'hbacsvcgroup' parameter.

This patch fixes the issue by using the CaseInsensitive comparator to
create the hbacsvcgroup list.

Tests were update to make sure a regression is not included in the
future.