P2PServer: added 1 second grace time for stale shares

Only for shares that lag 1 Monero block behind

src/p2pool.cpp

@@ -176,6 +176,7 @@ void p2pool::handle_miner_data(MinerData& data)
 	}
 
 	data.tx_backlog.clear();
+	data.time_received = std::chrono::system_clock::now();
 	m_minerData = data;
 	m_updateSeed = true;
 	update_median_timestamp();