duplicate torrents in the list when adding from the command line

[Jonathan McDougall]

Starting baretorrent with a torrent on the command line (such as from a browser or opening an associated file) fills the list twice. Switching to another category and back fixes it.

Looks like torrent_list::rebuild() is called from main_window::handle_new_files(), which fills in the entire list, but then the callbacks from libtorrent that torrents were added to the manager are fired, adding duplicate items. I'm not entirely sure what changed, but it's probably related to https://bazaar.launchpad.net/~jonathanmcdougall/baretorrent/trunk/revision/558.

[Jonathan McDougall (jonathanmcdougall)]

https://bazaar.launchpad.net/~jonathanmcdougall/baretorrent/trunk/revision/569