burn: Use user runtime dir instead of /tmp
burn: Use user runtime dir instead of /tmp

https://bugzilla.gnome.org/show_bug.cgi?id=646391

Signed-off-by: Tomas Bzatek <d3a1cc6aceb7629c6bc23f72976a8a12cdfc8825@redhat.com>

philipl/gvfs,xkahn/gvfs-cmis,halfline/gvfs,xkahn/gvfs-cmis,philipl/gvfs,xkahn/gvfs-cmis,halfline/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,gicmo/gvfs,gicmo/gvfs,gicmo/gvfs,halfline/gvfs,philipl/gvfs