0rtt takes 15 seconds to switch to a new path

[Arqu]

This surfaced when fixing the 0rtt flakes in https://github.com/n0-computer/iroh/pull/3496 Originally the PR also invalidated old paths for the same IP when a new one is encountered, which happened if you restarted the server and tried to re-connect.

However that turned out to be a bit risky as we don't have a complete understanding of possible side effects so that part of the PR was reverted. Keeping this issue up so we can follow up.

Reference code https://github.com/n0-computer/iroh/pull/3496/commits/110fb337de86031f2847adc4987aad589dbe6f3d