Removes two methods not used:
* _get_all_segmentation_ids
* _validate_vlan_id
About log formatting:
* In the __init__, '\n' can be removed from this line:
LOG.debug(_("Loaded device plugin %s\n"),
Closes-Bug: 1180783
Change-Id: Ic0aea7e8016f198e2ba245c710e12bc490720039