Display a debug report at the console if there are p2p sessions active while closing the last switchboard

[diederik]

When a switchboard connection closes, WLM keeps the P2P sessions in it's memory. We don't, since the sessions become useless anyway. To support unforseen cases, we should display some report (objects + states) of all disposed p2p applications.

Note that WLM could send a BYE much later when a switchboard connection is up again. By logging the dispose actions, we can find out much better why the next messages fail.