Automatic merge from submit-queue

Pass whole PVC to provisioner plugins

Gluster provisioner is interested in namespace of PVCs that are being provisioned and I don't want to add at as a new field in `volume.VolumeOptions` - it would contain almost whole PVC.

Let's rework `VolumeOptions` and pass direct reference to PVC there instead of some "interesting" fields and let the provisioner to pick information it is interested in.

There was lot of refactoring in volume plugins to apply this change (too many plugins), however the logic is simple and it's all the same in all plugins.

@rootfs @humblec