fix: cleaning up connected clients upon shutdown [MTT-1573] (#1945)

* chore: cleaning up connected clients upon shutdown [MTT-1573]

* chore: cleaning up connected clients upon shutdown [MTT-1573] changelog

* Update com.unity.netcode.gameobjects/CHANGELOG.md

Co-authored-by: Fatih Mar <mfatihmar@gmail.com>

Author: jeffreyrainy

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -10,6 +10,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 - Fixed: Hosting again after failing to host now works correctly
 
+- Fixed NetworkManager to cleanup connected client lists after stopping (#1945)
 - Fixed: NetworkHide followed by NetworkShow on the same frame works correctly (#1940)
 
 ## [1.0.0-pre.8] - 2022-04-27

com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs

@@ -765,12 +765,7 @@ private void Initialize(bool server)
 #endif
             LocalClientId = ulong.MaxValue;
 
-            PendingClients.Clear();
-            m_ConnectedClients.Clear();
-            m_ConnectedClientsList.Clear();
-            m_ConnectedClientIds.Clear();
-            LocalClient = null;
-            NetworkObject.OrphanChildren.Clear();
+            ClearClients();
 
             // Create spawn manager instance
             SpawnManager = new NetworkSpawnManager(this);
@@ -862,6 +857,16 @@ private void Initialize(bool server)
             NetworkConfig.NetworkTransport.Initialize(this);
         }
 
+        private void ClearClients()
+        {
+            PendingClients.Clear();
+            m_ConnectedClients.Clear();
+            m_ConnectedClientsList.Clear();
+            m_ConnectedClientIds.Clear();
+            LocalClient = null;
+            NetworkObject.OrphanChildren.Clear();
+        }
+
         /// <summary>
         /// Starts a server
         /// </summary>
@@ -1301,6 +1306,8 @@ internal void ShutdownInternal()
             IsListening = false;
             m_ShuttingDown = false;
             m_StopProcessingMessages = false;
+
+            ClearClients();
         }
 
         // INetworkUpdateSystem