Fix ident race condition

This creates an entry for the port as soon as the socket is opened,
without duplicates. This allows an identd service to respond correctly
if a request is received before the SSL handshake has finished and been
processed on our side.

Since socketOpen is not used in the project, it is removed here.
Since the only usage of socketInitialized(...) is with oidentd, its
semantic meaning is slightly changed to occur earlier, like socketOpen,
but only once, like the former socketInitialized(...).