Fixed wrong constructionyard placing on map brimstone

Also removed that [stuff](https://github.com/abcdefg30/OpenRA/commit/128ae6e1b7ec607cecf5dcaf9c0ccfd64271e8cf#diff-609fc603082ce4fbd779c785262f52d4L642), because it broke the map:
![brimstonebug](https://cloud.githubusercontent.com/assets/7704140/4430792/caf7cee8-4645-11e4-9019-06dea5602653.png)

Would fix #5788 .