fix(SnapDropZone): ensure force snap object state is saved correctly

There was an issue with the Snap Drop Zone that if on scene load an
interactable object was to be snapped to it, the order of load would
mean that the interactable object would not have completed set up
and therefore would not save the state of the interactable object
on force snap.

The fix is to ensure all force snaps happen at end of frame, removing
any race conditions with script load order.

Author: thestonefox

Assets/VRTK/Prefabs/Resources/Scripts/VRTK_SnapDropZone.cs

@@ -182,17 +182,12 @@ public virtual void ForceSnap(GameObject objectToSnap)
             VRTK_InteractableObject ioCheck = objectToSnap.GetComponentInParent<VRTK_InteractableObject>();
             if (ioCheck != null)
             {
-                ioCheck.SaveCurrentState();
                 StopCoroutine("AttemptForceSnapAtEndOfFrame");
                 if (ioCheck.IsGrabbed())
                 {
                     ioCheck.ForceStopInteracting();
-                    StartCoroutine(AttemptForceSnapAtEndOfFrame(objectToSnap));
-                }
-                else
-                {
-                    AttemptForceSnap(objectToSnap);
                 }
+                StartCoroutine(AttemptForceSnapAtEndOfFrame(ioCheck));
             }
         }
 
@@ -684,10 +679,11 @@ protected virtual void AttemptForceSnap(GameObject objectToSnap)
             OnTriggerStay(objectToSnap.GetComponentInChildren<Collider>());
         }
 
-        protected virtual IEnumerator AttemptForceSnapAtEndOfFrame(GameObject objectToSnap)
+        protected virtual IEnumerator AttemptForceSnapAtEndOfFrame(VRTK_InteractableObject objectToSnap)
         {
             yield return new WaitForEndOfFrame();
-            AttemptForceSnap(objectToSnap);
+            objectToSnap.SaveCurrentState();
+            AttemptForceSnap(objectToSnap.gameObject);
         }
 
         protected virtual void ToggleHighlight(Collider collider, bool state)