move need_save_resume_data to when a piece is completed instead of when it's written to disk

src/torrent.cpp

@@ -739,8 +739,6 @@ namespace libtorrent
 		// add_piece() multiple times
 		if (picker().is_finished(block_finished)) return;
 
-		m_need_save_resume_data = true;
-
 		picker().mark_as_finished(block_finished, 0);
 	}
 	
@@ -2216,6 +2214,8 @@ namespace libtorrent
 				, index));
 		}
 
+		m_need_save_resume_data = true;
+
 		remove_time_critical_piece(index, true);
 
 		bool was_finished = m_picker->num_filtered() + num_have()