gallium/u_vbuf: use updated pipe_draw_start_count while using draw_vbo

gallium/u_vbuf: use updated pipe_draw_start_count while using draw_vbo

new_draw has updated draw count. Stale info in draw caused regression
with piglit gl-3.0-multidrawarrays-vertexid -indirect

fixes piglit test ./gl-3.0-multidrawarrays-vertexid -indirect

Fixes: 1cd455b17b7a ("gallium: extend draw_vbo to support multi draws")

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9656>