Neutron L2 configuration must be serialized differently depending on env version

[Aleksey Kasatkin]

Changes were made with regards to https://bugs.launchpad.net/fuel/+bug/1272349 must only affect 5.1 and higher environments.
Now they affect serialization of Neutron L2 configuration for all possible versions of envs.
It can lead to wrong networking configuration in 5.0-5.0.2 neutron-enabled envs when they are managed with 5.1 master node.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/117557

[Aleksey Kasatkin (alekseyk-ru)]

Didn't see actual problems on 2 envs of 2.
1. 5.0.2, centos/ha/neutron-vlan, 1ctrl + 1comp
2. 5.0.2, centos/non-ha/neutron-gre/cinder, 1ctrl + 1comp + 1cind

[Aleksey Kasatkin (alekseyk-ru)]

The problem arrives on update cluster created with 5.0 master node to 5.0.2 using new (5.1) master node.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/117557
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=0f642fca4372bfb1dad50d3c7a4ab89330ebdf23
Submitter: Jenkins
Branch: master

commit 0f642fca4372bfb1dad50d3c7a4ab89330ebdf23
Author: Aleksey Kasatkin <email address hidden>
Date: Thu Aug 28 19:36:37 2014 +0300

    Serialization of neutron attrs depends on environment version

    It is a quick 'dirty' fix for the issue.
    Versioning of serializer must be introduced to avoid such bugs in future.

    Closes-Bug: #1362659

    Change-Id: Ie25221a6125654bac1810aca4c1745a6c1716bab