Add regression test for teleporting between neighbouring regions on the same simulator

This adds a non-advertised wait_for_callback option in [EntityTransfer].  Default is always true.
Teleport tests disable the wait for callback from the destination region in order to run within a single thread.

OpenSim/Region/ClientStack/RegionApplicationBase.cs

@@ -111,7 +111,7 @@ namespace OpenSim.Region.ClientStack
                     server.Start();
                 }
             }
-
+            
             base.StartupSpecific();
         }