Refactoring of contrib.test_networks tests

Some simple refactoring of contrib.test_networks tests in order
to make it easier to share unittests between v2 and the v2.1 API
in a following changeset

Partially implements blueprint v2-on-v3-api

Change-Id: I87e475acdaabacdcceaaf73b3ad831292644d3c7
Remove unnecessary debug/info logs of normal API ops

There are some debug/info log messages about normal API operations
in each API method, but Nova WSGI framework has already output the
similar messages. So these messages are meaningless, and this patch
removes them.

Change-Id: Ifea3edd912ec80eed2869c3f97345d403ea96c89
Port os-networks plugin to v2.1(v3) infrastructure

Ports os-networks extension and adapts it to the v2.1/v3 API
framework. API behaviour is identical.

- unittest code modified to share testing with both v2/v2.1
- Adds expected error decorators for API methods

Partially implements blueprint v2-on-v3-api

Change-Id: I94b7b476cbb02725a396725a379417b64afd58a7
Cleanup tenant networks plugin config creation

Cleans up the os-tenant-networks plugin config creation.
Although written in a way that the config options could be
declared in multiple places in Nova this is no longer the case
and its not something we should do anyway.

This is some prep work before porting the plugin to the
v2.1 API

Partially implements blueprint v2-on-v3-api

Change-Id: I3b8b26035654f2482b3ba9561c404b6a437ec8a2
Add instance_group_get_by_instance to db.api

Add a new method to the db.api that lets you get an instance group by
instance UUID.

Change-Id: I3d2a019c8f97166ec55574c610d12f572afb2bd1
Related-bug: #1379451
Merge "Add instance_group_get_by_instance to db.api"
Merge "Refactoring of contrib.test_networks tests"
Merge "Port os-networks plugin to v2.1(v3) infrastructure"
Merge "Remove unnecessary debug/info logs of normal API ops"
Merge "Cleanup tenant networks plugin config creation"
Merge commit 'refs/changes/41/127941/2' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch