Workaround for LinkDiscovery issue when running multiple ONOS clusters

When multiple ONOS cluster is deployed and there are connectivity between ONOS clusters, LLDP/BDDP packet sent from one cluster confuses the cluster on the other end.

In the long run, link discovery should be secured or link discovery packet should contain cluster ID of some sort.

But as a first step, support for per-Port LinkDiscovery suppression is needed.

Note:

• LinkDiscovery code already support per-Port LinkDiscovery suppression based on specific annotation.
• We need to add a convenient way to add Port annotation via REST etc.
• Might want to also add CLI to enable/disable LLDP suppression