ConfigSync: call base methods, use if-else chain for IsServer/IsClient

This change is intended to unify the code flow and to reduce diff size
of the upcoming fixes.

Normally, you'd want to call base class methods before your subclass
logic to avoid working with a partially initialized state.

Even though currently ConfigSyncBehaviour inherits directly from
NetworkBehaviour, whose corresponding methods are empty, any of this
might change in the future. So let's make the code more future-proof.

For the reference, these are the values of variables at runtime:

    Host:

    Awake   IsServer=False IsHost=False IsClient=False
    Spawn   IsServer=True IsHost=True IsClient=True
    Despawn IsServer=True IsHost=True IsClient=True

    Client (Join):

    Awake   IsServer=False IsHost=False IsClient=False
    Spawn   IsServer=False IsHost=False IsClient=True
    Despawn IsServer=False IsHost=False IsClient=True

Author: ratijas

CSync/CSync/Lib/ConfigSyncBehaviour.cs

@@ -53,6 +53,8 @@ private void Awake()
 
     public override void OnNetworkSpawn()
     {
+        base.OnNetworkSpawn();
+
         EnsureEntryContainer();
 
         if (IsServer)
@@ -77,10 +79,8 @@ public override void OnNetworkSpawn()
             }
 
             InitialSyncCompletedHandler?.Invoke(this, EventArgs.Empty);
-            return;
         }
-
-        if (IsClient)
+        else if (IsClient)
         {
             _syncEnabled.OnValueChanged += OnSyncEnabledChanged;
             _deltas.OnListChanged += OnClientDeltaListChanged;
@@ -96,6 +96,11 @@ public override void OnNetworkSpawn()
         }
     }
 
+    public override void OnNetworkDespawn()
+    {
+        base.OnNetworkDespawn();
+    }
+
     public override void OnDestroy()
     {
         DisableOverrides();