llvmpipe: Ensure outdated framebuffer state is not reused in lp_setup_bind_framebuffer().

llvmpipe: Ensure outdated framebuffer state is not reused in lp_setup_bind_framebuffer().

We were starting a scene whenever lp_setup_get_vertex_info() was called by
the draw module. So when when all primitives were culled/clipped, not only
did we create a new scene for nothing, but we end up using the old scene
with the old framebuffer state instead of a new one.

Fix consists in:
- don't call lp_setup_update_state() in lp_setup_get_vertex_info() -- no
  longer necessary
- always setting the scene state before binning a command -- query
  commands were bypassing it
- assert no old scene is reused in lp_setup_bind_framebuffer()