Ironic:  Fix direct use of flavor and instance module objects

This replaces all uses of nova.objects.flavor_obj.Flavor* with
nova.objects.Flavor* and nova.objects.instance_obj.Instance* with
nova.objects.Instance*

This work was done throughout Nova. An example of this is
commit 3c1085f528596089a638ac3bb44a9ed3e201e62f.

Change-Id: I8f2dbb408acbdf8124bc141925de03ce6f12bd91
Merge "Ironic:  Fix direct use of flavor and instance module objects"