CF-118 None values in cinder DB
CF-118 None values in cinder DB

Replaces invalid python `None` values with `NULL`.

MirantisWorkloadMobility/CloudFerry,SVilgelm/CloudFerry,mgrygoriev/CloudFerry,MirantisWorkloadMobility/CloudFerry,mgrygoriev/CloudFerry,MirantisWorkloadMobility/CloudFerry,SVilgelm/CloudFerry,SVilgelm/CloudFerry,MirantisWorkloadMobility/CloudFerry,mgrygoriev/CloudFerry,mgrygoriev/CloudFerry,SVilgelm/CloudFerry