Controller does not start up properly when it is used in a specific sequence with mininet

1. Start up the controller

2. From mininet populate a topology

3. Shut down the controller (Exit with Ctrl + C)

4. In mininet exit the CLI (thus tearing down the toplogy)

5. Start up the controller - you will see a bunch of exceptions - the controller will not be functional at this point

(See attached file out.txt for the exceptions)