Replace panic with error in network lib.rs

[thibault-martinez]

thread 'main' panicked at 'Fatal error: Binding to /ip4/0.0.0.0/tcp/15600 failed.', /var/lib/bee/bee-network/src/lib.rs:100:9

[Alex6323]

I would just let the node panic tbh if it can't acquire a binding to that address (e.g. no network interface, or port already in use)