player/Control: move IDLE_PLAYER to Player::SeekDecoder()

NEWS

 ver 0.20.23 (not yet released)
+* protocol
+  - emit "player" idle event when restarting the current song
 * new clang crash bug workaround
 
 ver 0.20.22 (2018/10/23)

src/player/Control.cxx

@@ -246,12 +246,8 @@ PlayerControl::LockSeek(DetachedSong *song, SongTime t)
 {
 	assert(song != nullptr);
 
-	{
-		const std::lock_guard<Mutex> protect(mutex);
-		SeekLocked(song, t);
-	}
-
-	idle_add(IDLE_PLAYER);
+	const std::lock_guard<Mutex> protect(mutex);
+	SeekLocked(song, t);
 }
 
 void

src/player/Thread.cxx

@@ -580,6 +580,8 @@ Player::SeekDecoder()
 {
 	assert(pc.next_song != nullptr);
 
+	idle_add(IDLE_PLAYER);
+
 	pc.outputs.Cancel();
 
 	const SongTime start_time = pc.next_song->GetStartTime();