Fix llAttachToAvatar()

Apart from one obvious bug, this was failing because attempting to serialize the script from inside the script (as part of saving the attachment as an inventory asset) was triggering an extremely long delay.
So we now don't do this.  The state will be serialized anyway when the avatar normally logs out.
The worst that can happen is that if the client/server crashes, the attachment scripts start without previous state.

OpenSim/Region/ScriptEngine/Interfaces/IScriptInstance.cs

@@ -58,7 +58,11 @@ namespace OpenSim.Region.ScriptEngine.Interfaces
     /// </summary>
     public interface IScriptInstance
     {
+        /// <summary>
+        /// Is this script currently running?
+        /// </summary>
         bool Running { get; set; }
+
         bool ShuttingDown { get; set; }
         string State { get; set; }
         IScriptEngine Engine { get; }
@@ -78,7 +82,14 @@ namespace OpenSim.Region.ScriptEngine.Interfaces
 
         void Init();
         void Start();
+
+        /// <summary>
+        /// Stop the script.
+        /// </summary>
+        /// <param name="timeout"></param>
+        /// <returns>true if the script was successfully stopped, false otherwise</returns>
         bool Stop(int timeout);
+
         void SetState(string state);
 
         void PostEvent(EventParams data);