Bugfix: do not keep relaying spent wallet transactions

The original test (checking whether the transaction occurs in the
txindex) is not usable anymore, as it will miss anything already
fully spent. However, as merkle transactions (and by extension,
wallet transactions) track which block they were last seen being
included in, we can use that to determine the need for
rebroadcasting.

src/wallet.cpp

@@ -820,21 +820,17 @@ void CWallet::ReacceptWalletTransactions()
 
 void CWalletTx::RelayWalletTransaction()
 {
-    CCoinsViewCache& coins = *pcoinsTip;
     BOOST_FOREACH(const CMerkleTx& tx, vtxPrev)
     {
-        if (!tx.IsCoinBase())
-        {
-            uint256 hash = tx.GetHash();
-            if (!coins.HaveCoins(hash))
-                RelayMessage(CInv(MSG_TX, hash), (CTransaction)tx);
+        if (!tx.IsCoinBase()) {
+            if (tx.GetDepthInMainChain() == 0)
+                RelayMessage(CInv(MSG_TX, tx.GetHash()), (CTransaction)tx);
         }
     }
     if (!IsCoinBase())
     {
-        uint256 hash = GetHash();
-        if (!coins.HaveCoins(hash))
-        {
+        if (GetDepthInMainChain() == 0) {
+            uint256 hash = GetHash();
             printf("Relaying wtx %s\n", hash.ToString().substr(0,10).c_str());
             RelayMessage(CInv(MSG_TX, hash), (CTransaction)*this);
         }