Bin/Node: Prevent stall connections

What

Ensure P2P connections are closed when the DAL node is shut down via Ctrl+C.

Why

Otherwise, we observe stall connections that are not closed by the attester since it does not send TPC close messages when the DAL node exits.

How

Call P2p.shutdown.

How to test

• Run a DAL node in attester profile
• Run a DAL node in any other mode and connect it to your attester node
• Kill the other DAL node with Ctrl+C
• Observe on master a stall connection from the other node, and not with this patch (may not be deterministic)