Fix speed modifiers for spells Permafrost, Improved Curse of Exhaustion,...

... Camouflage, Pathfinding, Amplify Curse, Cheetah Sprint

This is a hack way, but the other way I can not see because the error is in the DBC. This can be seen when you compare DBC with next patch.

This commit [5a5169b](http://github.com/mangos-zero/server-old/commit/5a5169b) is one of those pending backports from old mangos-zero concatenated in: https://github.com/cmangos/issues/wiki/classic_backporting-todo-zero-commits

I tested it and this is my report:
> I've tested this one and I do see some improvements. However, the original author did not think it was the proper way to fix it. I don't know either. In a nutshell: fix needed and working but maybe not proper.

Maybe this could be discussed with @sidsukana ?