check if we should avoid transaction message which we have already seen

[kishansagathiya]

Issue summary

• check if hasSeen should be move before handle transaction

• gossamer/dot/network/transaction.go

  Lines 130 to 140 in afb2151

  	propagate, err := s.handleTransactionMessage(txnMsg.peer, txnMsg.msg)
  	if err != nil {
  	s.host.closeProtocolStream(protocolID, txnMsg.peer)
  	continue
  	}
  	if s.noGossip || !propagate {
  	continue
  	}
  	if !s.gossip.hasSeen(txnMsg.msg) {

• https://github.com/ChainSafe/gossamer/pull/2435/files/47f2d110025aa76a6893b37d1e6246148528089a#diff-a18642ae37437d1628a430b03a8ce276b5803e81f9b6a43f8f508fe4cfd0c322

Other information and links

• fix(dot/netwok): check for duplicate message earlier #2435

[timwu20]

this looks like a good change, but we should cross reference what substrate does.