Add --force flag to "kick user" console command to allow bypassing of recent race condition checks.

This is to allow a second attempt to remove an avatar even if "show connections" shows them as already inactive (i.e. close has already been attempted once).
You should only attempt --force if a normal kick fails.
This is partly for diagnostics as we have seen some connections occasionally remain on lbsa plaza even if they are registered as inactive.
This is not a permanent solution and may not work anyway - the ultimate solution is to stop this problem from happening in the first place.

OpenSim/Tests/Common/Mock/TestClient.cs

@@ -933,6 +933,11 @@ namespace OpenSim.Tests.Common.Mock
         }
 
         public void Close()
+        {
+            Close(false);
+        }
+
+        public void Close(bool force)
         {
             // Fire the callback for this connection closing
             // This is necesary to get the presence detector to notice that a client has logged out.