Give peers one timer tick to finish handshake before disconnecting

Give peers one timer tick to finish handshake before disconnecting

This ensures we don't let a hung connection stick around forever if
the peer never completes the initial handshake.

This also resolves a race where, on receiving a second connection
from a peer, we may reset their_node_id to None to prevent sending
messages even though the `channel_encryptor`
`is_ready_for_encryption()`. Sending pings only checks the
`channel_encryptor` status, not `their_node_id` resulting in an
`unwrap` on `None` in `enqueue_message`.