JSON Schema use validator (draft3 or draft4) to validate the
given schema against given instance.
By default it use draft4 validator which is current one. If new validator
will be released in future and that become default then, there might be some
compatibility issues between draft4 and new version.
For example from draft3 to draft4, 'ip-version' format has been changed to 'ipv4'.
This commits explicitly pass the validator while doing the schema validation.
Also adds unit tests to check the current version of validator.
If any new validator will be available in future, then we can use that by doing
proper modification in schema files if needed.
Change-Id: Ie11e3ba60926f247a82670b7da37d7890d16280c
7c2ad79c30