Fix pre-noise outbound peer disconnect panic found by fuzzer

Fix pre-noise outbound peer disconnect panic found by fuzzer

If we make an outbound connection to a peer who we are already
connected to, and the outbound connection fails
pre-noise-completion, we will remove the original peer connection
from our node_id_to_descriptor map.

The fuzzer managed to find this by crashing in Channel's assertions
that we don't do a get_channel_reestablish() when the Channel isn't
already marked disconnected.