'Return scsi controller or None based on image meta'

@staticmethod
def _get_scsi_controller(image_meta):

    if image_meta.properties.get('hw_scsi_model'):
        hw_scsi_model = image_meta.properties.hw_scsi_model
        scsi_controller = vconfig.LibvirtConfigGuestController()
        scsi_controller.type = 'scsi'
        scsi_controller.model = hw_scsi_model
        scsi_controller.index = 0
        return scsi_controller
