core: List/report all transfers
core: List/report all transfers

'TransferIDs' state variable should list IDs for all transfers we have,
even the ones that are complete.

GNOME/rygel,Tarnyko/rygel,GNOME/rygel,jku/rygel,Tarnyko/rygel,luisbg/rygel,Pelagicore/Media-Manager-Rygel-patched,Pelagicore/Media-Manager-Rygel-patched,jku/rygel,GNOME/rygel,Pelagicore/Media-Manager-Rygel-patched