Synnefo

Fix compatibility issues with factory_boy

Update models_factory to use factory.DjangoModelFactory instead of
factory.Factory.

Create public NIC when creating VM

Until now, a server's public NetworkInterface was not created in the DB
until the arrival of the message from Ganeti hooks. However, the IPv4
address of the NIC is reserved before sending the OP_INSTANCE_CREATE
job to Ganeti....

Add object factories for most db models

Use 'factory_boy' library for creating Django ORM objects as test data.
These factories can be used as fixtures replacement since they are
easier to write and maintain.