Make catch-up spectator clocks running state immutable externally

osu.Game/Screens/OnlinePlay/Multiplayer/Spectate/CatchUpSpectatorPlayerClock.cs

@@ -34,6 +34,16 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer.Spectate
 
         public void Stop() => IsRunning = false;
 
+        void IAdjustableClock.Start()
+        {
+            // Our running state should only be managed by an ISyncManager, ignore calls from external sources.
+        }
+
+        void IAdjustableClock.Stop()
+        {
+            // Our running state should only be managed by an ISyncManager, ignore calls from external sources.
+        }
+
         public bool Seek(double position)
         {
             CurrentTime = position;

osu.Game/Screens/OnlinePlay/Multiplayer/Spectate/CatchUpSyncManager.cs

@@ -144,6 +144,8 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer.Spectate
                 // Make sure the player clock is running if it can.
                 if (!clock.WaitingOnFrames.Value)
                     clock.Start();
+                else
+                    clock.Stop();
 
                 if (clock.IsCatchingUp)
                 {

osu.Game/Screens/OnlinePlay/Multiplayer/Spectate/ISpectatorPlayerClock.cs

@@ -11,6 +11,16 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer.Spectate
     /// </summary>
     public interface ISpectatorPlayerClock : IFrameBasedClock, IAdjustableClock
     {
+        /// <summary>
+        /// Starts this <see cref="ISpectatorPlayerClock"/>.
+        /// </summary>
+        new void Start();
+
+        /// <summary>
+        /// Stops this <see cref="ISpectatorPlayerClock"/>.
+        /// </summary>
+        new void Stop();
+
         /// <summary>
         /// Whether this clock is waiting on frames to continue playback.
         /// </summary>