DB connection error handling

If DB client can not connect to database, the following error gets raised:
```
raise OSError('Multiple exceptions: {}'.format(
OSError: Multiple exceptions: [Errno 111] Connect call failed ('127.0.0.1', 5445), [Errno 99] Cannot assign requested address
```

This error is not handled. The API will return 500 status code. The dashboard does not handle this status code and spins indefinitely.