Added knownRemotes to DaemonStatus. This list is not entirely trivial to
calculate, and having it here should make it easier to add/remove remotes
on the fly later on. It did require plumbing the daemonstatus through to
some more threads.
SampleMVar won't work; between getting the current value and changing
it, another thread could made a change, which would get lost.
TMVar works well; this update situation is handled by atomic transactions.
