M_StartControlPanel: Guarantee titlemap contexts have internal server stopped when entering menu

Guarantees netUnlocked is correctly updated in most contexts, since that's dependent on SV_ResetServer, which isn't called if a server is running
Also guarantees titlemapinaction isn't true during regular play

src/d_clisrv.c

@@ -3927,6 +3927,7 @@ void SV_StopServer(void)
 	maketic = gametic+1;
 	neededtic = maketic;
 	serverrunning = false;
+	titlemapinaction = false;
 }
 
 // called at singleplayer start and stopdemo

src/k_menufunc.c

@@ -726,6 +726,14 @@ void M_StartControlPanel(void)
 	{
 		if (gamestate != GS_MENU)
 		{
+			if (titlemapinaction)
+			{
+				// We clear a LITTLE bit of state, but not a full D_ClearState.
+				// Just enough to guarantee SV_ResetServer is called before session start.
+				SV_StopServer();
+				SV_ResetServer();
+			}
+
 			G_SetGamestate(GS_MENU);
 
 			gameaction = ga_nothing;