Don't set m_LastPacketTimestamp on handshake when we are connected (#513)

If another tracker is trying to find the server, they will send the
handshake packet to the whole network, which prevents us from realising
if the connection to server has timed out.

Author: ImSapphire

src/network/connection.cpp

@@ -664,7 +664,6 @@ void Connection::update() {
 		return;
 	}
 
-	m_LastPacketTimestamp = millis();
 	int len = m_UDP.read(m_Packet, sizeof(m_Packet));
 
 #ifdef DEBUG_NETWORK
@@ -679,6 +678,12 @@ void Connection::update() {
 	(void)packetSize;
 #endif
 
+	if (static_cast<ReceivePacketType>(m_Packet[3]) == ReceivePacketType::Handshake) {
+		m_Logger.warn("Handshake received again, ignoring");
+		return;
+	}
+
+	m_LastPacketTimestamp = millis();
 	switch (static_cast<ReceivePacketType>(m_Packet[3])) {
 		case ReceivePacketType::HeartBeat:
 			sendHeartbeat();
@@ -688,8 +693,7 @@ void Connection::update() {
 			break;
 
 		case ReceivePacketType::Handshake:
-			// Assume handshake successful
-			m_Logger.warn("Handshake received again, ignoring");
+			// handled above
 			break;
 
 		case ReceivePacketType::Command: