error details are missed when CB return BadRequest to v2.batchUpdate 

When  v2.batchUpdate gets a BadRequest from ContextBroker, the empty details are returning, and we just know that a BadRequest was retrieved but without any description or reason.


Similar issue:  https://github.com/Ficodes/ngsijs/issues/20


Related with https://github.com/telefonicaid/perseo-fe/issues/788