Added checks to see if ip, network_id & bootable assigned to interface.
Added checks to see if ip, network_id & bootable assigned to interface.

These fields are nullable, and pb doesn't like having None assigned to an int32 field.

stdweird/aquilon,guillaume-philippon/aquilon,stdweird/aquilon,guillaume-philippon/aquilon,guillaume-philippon/aquilon,quattor/aquilon,stdweird/aquilon,quattor/aquilon,quattor/aquilon