Blender Git Loki

Fix typo made back in svn rev35785

Callback handle was assigning to wrong storage in RE_draw_lock_cb.
So far it was completely harmless because all the callbacks are
using the same handle, so test_break_callback was using correct
handle, and since draw_lock_callback didn't use handle at all
nobody noticed this.

But this typo lead to draw_lock_callback using NULL instead of
real RenderJob, which is bad for the feature we're working in
GSoC branch.