Remember the address used when connecting to an inviting node.

The inviter sends us its own host config file, which should be populated
with its known addresses. However, if a symbolic hostname is in the
invitation URL and it can resolve to multiple IP addresses, or if the IP
address associated with it is currently different from when the invitation
was generated, the address used to connect to the inviter might not be
present in its host config file. This could cause the invitation to succeed,
but then the nodes would fail to make a regular MeshLink connection.