make sure that we don't find the wrong shares if a user and a group have the same ID
make sure that we only find the shares from the correct share type if users and groups with the same ID exists
use the new base class for unit tests
only users can have a display name different from the id
Merge pull request #12224 from owncloud/fix_12211

make sure that we don't find the wrong shares if a user and a group have the same ID