Fix map hardness under nanoframes

[GoogleFrog]

There is a gadget which changes the terrain type under unit nanoframes, to make them impassible. The hardness of arbitrary terrain cannot be controlled. See:

• https://github.com/ZeroK-RTS/Zero-K/commit/32b94f4ae033068cea9ee6e2374235083ba9ea60
• https://springrts.com/mantis/view.php?id=5790

[sprunk]

hay gurl, are you a nanoframe? cause i cant control my hardness

The terraintype solution was reverted so this is no longer a problem: https://github.com/ZeroK-RTS/Zero-K/commit/a3131e722620ab020b5d9b775ef4a648947fa96c

The engine also now allows controlling hardness if we need it for other use: https://github.com/spring/spring/commit/845701ba97edf31aa94460fdd4cf239132b1dc1d

[GoogleFrog]

Note that using that engine is infeasible for the foreseeable future.