Make neutronapi use NetworkRequest for allocate_for_instance()

This makes the neutronapi code use the NetworkRequest object for
the allocate_for_instance() operation. It also prepares validate_networks()
by using the object internally, which will make it easier when we
actually start passing that from the caller.

Change-Id: I71c85ed4124e1e00b8c4c6d8dc02f2f280d69cfa
Change v3 quota-sets API to v2.1

This patch changes v3 quota-sets API to v2.1 and makes v2 unit tests
share between v2 and v2.1.

The differences between v2 and v3 are described on the wiki page
https://wiki.openstack.org/wiki/NovaAPIv2tov3 .

Partially implements blueprint v2-on-v3-api

Change-Id: I96377c2c5c02e00cb70eadde225f3e17d0e0025c
Merge "Change v3 quota-sets API to v2.1"
Merge "Make neutronapi use NetworkRequest for allocate_for_instance()"