Use whilte list filtering for collected oswl info

[Artem Roma]

Now for retrieving/filtering of particular attributes from collected oswl resource instance custom code is implemented. This code has some limitation in case we need to do some sophisticated processing of attributes (e.g. filtering by keys for nested dict attributes). In order to avoid that limitation and make different parts of statistics code more consistent white list filtering mechanism that is using for building info about installation ([1], [2]) should be reused in oswl collecting code.

[1]: https://github.com/stackforge/fuel-web/blob/master/nailgun/nailgun/statistics/installation_info.py#l30-l58
[2]: https://github.com/stackforge/fuel-web/blob/master/nailgun/nailgun/statistics/installation_info.py#l126-l136

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/169328

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/169328
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=c47ba89597bff04d76c5d82bb8a918507dfc0a3e
Submitter: Jenkins
Branch: master

commit c47ba89597bff04d76c5d82bb8a918507dfc0a3e
Author: Artem Roma <email address hidden>
Date: Tue Mar 31 17:16:09 2015 +0300

    White list filtering reused for oswl collecting

    Change-Id: I6177cbf83079b89ad25bd8a1ca5072d0e1c027ab
    Closes-Bug: #1438716