Fix bug where removing a physical linkset would only decrement the Active Objects statistic by 1 instead of by the number of prims removed.

Unlike LL, OpenSimulator currently uses this stat to record the number of prims in the physics simulation, even when they are at rest.
Added regression test for this case.

OpenSim/Region/Framework/Scenes/SceneGraph.cs

@@ -519,12 +519,12 @@ namespace OpenSim.Region.Framework.Scenes
 
         protected internal void AddPhysicalPrim(int number)
         {
-            m_physicalPrim++;
+            m_physicalPrim += number;
         }
 
         protected internal void RemovePhysicalPrim(int number)
         {
-            m_physicalPrim--;
+            m_physicalPrim -= number;
         }
 
         protected internal void AddToScriptLPS(int number)

OpenSim/Region/Framework/Scenes/Tests/SceneStatisticsTests.cs

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the OpenSimulator Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using NUnit.Framework;
+using OpenMetaverse;
+using OpenSim.Framework;
+using OpenSim.Framework.Communications;
+using OpenSim.Region.Framework.Scenes;
+using OpenSim.Tests.Common;
+using OpenSim.Tests.Common.Mock;
+
+namespace OpenSim.Region.Framework.Scenes.Tests
+{
+    [TestFixture]
+    public class SceneStatisticsTests : OpenSimTestCase
+    {
+        private TestScene m_scene;
+
+        [SetUp]
+        public void Init()
+        {
+            m_scene = new SceneHelpers().SetupScene();
+        }
+
+        [Test]
+        public void TestAddRemovePhysicalLinkset()
+        {
+            Assert.That(m_scene.SceneGraph.GetActiveObjectsCount(), Is.EqualTo(0));
+
+            UUID ownerId = TestHelpers.ParseTail(0x1);
+            SceneObjectGroup so1 = SceneHelpers.CreateSceneObject(3, ownerId, "so1", 0x10);
+            so1.ScriptSetPhysicsStatus(true);
+            m_scene.AddSceneObject(so1);
+
+            Assert.That(m_scene.SceneGraph.GetTotalObjectsCount(), Is.EqualTo(3));
+            Assert.That(m_scene.SceneGraph.GetActiveObjectsCount(), Is.EqualTo(3));
+
+            m_scene.DeleteSceneObject(so1, false);
+
+            Assert.That(m_scene.SceneGraph.GetTotalObjectsCount(), Is.EqualTo(0));
+            Assert.That(m_scene.SceneGraph.GetActiveObjectsCount(), Is.EqualTo(0));
+        }
+    }
+}