#OBS-I116: Dataset CRUD apis test fixes

[JeraldJF]

Description
Fixes:

1. On check for dataset exists, if not exists the dataset.id is null so its replaced by datasetId
2. api_version must be fetched from the datasets, as there are checks on api_version in the line 40.
3. Replaced _.map with for of as maps do not support async calls.
4. Check for isEmpty for denorm fields and transformations as both can be empty array.
5. Modifying datafields with the transformations on it.
6. entry_topic column added to Dataset models.