Qbsp: brush entity with "origin" key causes leak

[ericwa]

*** WARNING 10: Reached occupant "func_detail_wall" at (4480 0 0), no filling performed.

// entity 411
{
"classname" "func_detail_wall"
"origin" "4480 0 0"
"angle" "180"
"_tb_group" "64442"
// brush 0
{

This should be recognized as a brush entity, and not used for leak detection.