Controller loses file information if restarted

[ammuaj]

Though the file chunks are available in cunk servers, the controller loses the file and chunk server information if it is restarted.

[menuka94]

In a real-world file system, the metadata needs to be stored in persistent storage along with data so that the ChunkServers can be stateless. This wouldn't be part of the testing scenarios for the assignment, so we can decide if we want to implement this, as time permits.