Federation bug fixes

Some issues were found with multiple federated supernodes and how they
handled edges moving between them.

These issues would result in occasional loss of connectivity between
edges connected via different supernodes.

• Federated MAC addresses would regularly be timed out and deleted due to a
  faulty "last_seen" update.
• Federated supernodes would have trouble registering due to a bad boolean
  conversion.
• Some additional refactoring and monitoring was also added while tracking
  these down.