- Add separate priority event queue for events that must be processed

- Add separate priority event queue for events that must be processed
  even when worker is paused (e.g. interface reconfiguration). This is
  needed to prevent deadlocks when reconfiguring interfaces - as network
  manager is paused then, but we still need to stop/start listening.

- Proper handling of TCP listen errors in netmgr - bind to the socket first,
  then return the error code.