CFY-1215

Manually tested for basic functionality. Used https://github.com/achirko/cloudify-openstack-plugin/blob/dev/plugin.yaml as plugin definition and https://github.com/achirko/cloudify-openstack-plugin/blob/dev/blueprint.yaml as a base for testing.
Please use these two decorators as:
@operation & @with_cinder_client
For being aligned with the rest of our plugins.

In the future we might have something like:
@cloudify.operation