Have some activities count as idle activities

OpenRA.Game/Activities/Activity.cs

@@ -152,6 +152,7 @@ namespace OpenRA.Activities
 			set { NextActivity = value; }
 		}
 
+		public bool IsIdle { get; protected set; }
 		public bool IsInterruptible { get; protected set; }
 		public bool IsCanceled { get { return State == ActivityState.Canceled; } }
 

OpenRA.Game/Actor.cs

@@ -53,7 +53,7 @@ namespace OpenRA
 		public IOccupySpace OccupiesSpace { get; private set; }
 		public ITargetable[] Targetables { get; private set; }
 
-		public bool IsIdle { get { return CurrentActivity == null; } }
+		public bool IsIdle { get { return CurrentActivity == null || CurrentActivity.IsIdle; } }
 		public bool IsDead { get { return Disposed || (health != null && health.IsDead); } }
 
 		public CPos Location { get { return OccupiesSpace.TopLeft; } }

OpenRA.Mods.Common/Activities/Air/FlyCircle.cs

@@ -21,6 +21,7 @@ namespace OpenRA.Mods.Common.Activities
 
 		public FlyCircle(Actor self)
 		{
+			IsIdle = true;
 			plane = self.Trait<Aircraft>();
 			cruiseAltitude = plane.Info.CruiseAltitude;
 		}

OpenRA.Mods.Common/Activities/Air/HeliFlyCircle.cs

@@ -22,6 +22,7 @@ namespace OpenRA.Mods.Common.Activities
 		public HeliFlyCircle(Actor self)
 		{
 			helicopter = self.Trait<Aircraft>();
+			IsIdle = true;
 		}
 
 		public override Activity Tick(Actor self)