In logical_device_agent updateMeterTable need not call generateDeviceRoutesIfNeeded

The device routes are based on the NNI ports and UNI ports of the logical device and meter bands don't influence these. So there is no need to look for re-generation of the routes when the meters are manipulated.

As a result of this; when there is a single ONU and it gets deleted, ONOS tries to remove the meters, but this fails as the ports are not found and ONOS keeps on trying to remove these meters (please see attached logs)