Make networking API endpoints match schema

There used to be non-optional parameters with default values. And
not only that, the default values were mutable which is bad.

Patch Set 2:
- Rebased.

Change-Id: Ifee2318b89f190bffa4c8db65eae7839d21a3d29
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/15482
Reviewed-by: Giuseppe Vallarelli <gvallare@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>