glocalfile: Allow trashing only for locations supported by trash:///
New bugs appears periodically in nautilus/gvfs/glib components that not all trashed files are shown in trash:///. It used to be problem mostly for "bind mounts" and btrfs subvolumes only. Currently, it is also problem for nfs, cifs and other filesystems, which have been recently added by commmit 0d69462f on the list of system internal filesystems.
This happens because the trash backend doesn't monitor files on system internal mounts. Such behavior is not against the trash-spec, however, we should be consistent within GNOME.
This behavior has the nice side-effect that it solves issues with hangs on network filesystems: #605, because those are currently on the system internal filesystem list.