i965: Force even an empty query to flush all previous queries.

i965: Force even an empty query to flush all previous queries.

The specification requires that query results are processed in order, (when
one query result is returned, all previous query of the same type must also be
available). The implementation was failing this requirement in the case of
BeginQuery and EndQuery with no intervening drawing, (the result would be made
available immediately without flushing previous queries).

This fixes the following es3conform test:

	occlusion_query_query_order

as well as the following piglit test:

	occlusion_query_order

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>