sharing: Fix Bluetooth label always being off

https://bugzilla.gnome.org/show_bug.cgi?id=712252
sharing: Add more debug for duplicate folders
sharing: Make it possible to add new folders

The media panel wouldn't let you add more folder because the
test for equality was reversed.

https://bugzilla.gnome.org/show_bug.cgi?id=710580
sharing: Fix crash when turning off Sharing

Another fallout from:
05a4f6d3d9620782fa5d1a279ef84c11701247d1

https://bugzilla.gnome.org/show_bug.cgi?id=712338
sharing: Fix compile time warning

Another warning in cc_sharing_panel_add_folder()