network: always pass transactions to consensus process

Consensus can require conflicting transactions and it can require more
transactions than mempool can fit, all of this should work. Transactions will
be checked anyway using its secondary mempool. See the scenario from #668.

pkg/network/server.go

@@ -965,10 +965,10 @@ func (s *Server) handleTxCmd(tx *transaction.Transaction) error {
 	}
 	s.txInMap[tx.Hash()] = struct{}{}
 	s.txInLock.Unlock()
-	if s.verifyAndPoolTX(tx) == nil {
 	if s.txCallback != nil {
 		s.txCallback(tx)
 	}
+	if s.verifyAndPoolTX(tx) == nil {
 		s.broadcastTX(tx, nil)
 	}
 	s.txInLock.Lock()

pkg/network/server_test.go

@@ -474,9 +474,7 @@ func TestTransaction(t *testing.T) {
 		tx := newDummyTx()
 		s.chain.(*fakechain.FakeChain).PoolTxF = func(*transaction.Transaction) error { return core.ErrInsufficientFunds }
 		s.testHandleMessage(t, nil, CMDTX, tx)
-		for _, ftx := range s.services[0].(*fakeConsensus).txs {
-			require.NotEqual(t, ftx, tx)
-		}
+		require.Contains(t, s.services[0].(*fakeConsensus).txs, tx) // Consensus receives everything.
 	})
 }