Have nitriding fork after setup

[NullHypothesis]

It would be convenient to have nitriding fork once networking is all set up. That would allow enclave developers to write startup scripts like:

#!/bin/bash

# Invoke nitriding.
./nitriding -fqdn example.com

# Invoke the enclave application.
./enclave-app -foo -bar

Note the missing ampersand when starting nitriding. The enclave application will only run once nitriding has set up networking.