core: Error on 'background' request for streams
core: Error on 'background' request for streams

Throw an error on 'background' download request for streaming content.
This satisfies DLNA requirement 7.4.49.4.

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