Fix for py33 unittest running

Rework some imports to work with py27 and py33, also fix unittests
for config schemas and version checking. This commit is not garantee
that application will fully worked on python3.3
Task:
https://blueprints.launchpad.net/rubick/+spec/python33-support

Signed-off-by: Peter Lomakin <plomakin@mirantis.com>

Change-Id: Iffa564d52fd2bf83cebe9f31cca74e27c0b6baad