Provide mechnism to check status of all the dragondlow services across cluster

A mechanism could be provided to check status of all the services of Dragonflow across the cluster. It can help to provide status from a single point. One of the possible way to handle is

1) Whenever a service starts, it register itself in database.
2) Either of the following approach can be used
  - The service keeps on providing heartbeat
  - A separate thread can check these services
  - if database provide health monitoring then it can be used as well. For example consul provide a mechanism to provide health monitoring and key value store as well.
  - A hybrid approach can be used as well for example applications send heartbeat, if heartbeat is not received then service health can be checked explicitly and its status may be updated.