validates 4 fields only if its not a new record

## Status: ready to merge

Responsible: Andre Orvalho
Reported: Andre Orvalho
Relevant to: creating images

The on update validations were triggered when images were nested attributes and we were updating the parent object(Example: When adding a new image to an existing article). If the validations failed the before_create callbacks which set those values were never called and it failed. 

This is supposed to solve the problem