Closes rc/hpc-factory#181

Defining a network can be optional when a port is already defined when
deploying a VM.

This commit adds flexibility where you can either use --port or
--network options to define a network during the deployment.

Alternatively, you can define both but the port cannot be from the same
network you used in the --network option. Otherwise, you will have two
ips from the same network which will cause network reachability issues.