MountWatcher can't do this, because it uses the session dbus,
and won't have access to the new DBUS_SESSION_BUS_ADDRESS if a new session
is started.
Bumped dbus library version, FD leak in it is fixed.
Now when the dbus connection is dropped, it'll fall back to polling.
I could make it try to reconnect, but there's a FD leak in the dbus
library, so not yet.
This deals with interruptions in network connectevity, by listening
for a new network interface coming up (using dbus to see when
network-manager or wicd do it), and forcing a rescan of
