Fix Nova-net netowrk commands

In cleaning up functional tests for nova-net, I discovered some
problems in network create:
* --subnet option is required in network create command
* Switch API to use /os-networks rather than /os-tenant-networks as this
  is what we were actually using via novaclient
* Fix functional tests for nova-net
* Normalize some private function names in network/v2/network.py

Change-Id: I426b864406756d58d140575a3a45ee9aee67ce84

doc/source/backwards-incompatible.rst

@@ -30,7 +30,13 @@ Backwards Incompatible Changes
 Release 3.10
 ------------
 
-1. The positional argument ``<snapshot-name>`` of the ``volume snapshot create``
+1. The ``network create`` command now requires the ``--subnet`` option when used
+   with Nova-network clouds.
+
+  * As of: 3.10
+  * Commit: https://review.openstack.org/460679
+
+2. The positional argument ``<snapshot-name>`` of the ``volume snapshot create``
    command is no longer optional.
 
    Previously when the ``--volume`` option was

doc/source/command-objects/network.rst

@@ -71,6 +71,8 @@ Create new network
 
     Set network description
 
+    *Network version 2 only*
+
 .. option:: --availability-zone-hint <availability-zone>
 
     Availability Zone in which to create this network