Standarize ip validation along the code

Details:
 - Use the nova/utils.py validations along the code
 - refactor ipv4 validator to looks like ipv6 validator
 - interprets ip validations exceptions as Invalid IP values

Change-Id: Ia506c00510a066e167d3dcd9dd371a371129a9dd
Merge "Standarize ip validation along the code"