added a random delay before repathing (tunable per-unittype in Mobile). fixes a lot of pathological pathing perf.

OpenRA.Game/Traits/Mobile.cs

@@ -26,6 +26,8 @@ namespace OpenRA.Traits
 	public class MobileInfo : ITraitInfo
 	{
 		public readonly UnitMovementType MovementType = UnitMovementType.Wheel;
+		public readonly int WaitAverage = 60;
+		public readonly int WaitSpread = 20;
 
 		public object Create(Actor self) { return new Mobile(self); }
 	}