Merge bitcoin#11738: Fix sendrawtransaction hang when sending a tx al…

…ready in mempool

d9340ce Fix sendrawtransaction hang when sending a tx already in mempool (Matt Corallo)

Pull request description:

  I assume this is what bitcoin#11721 actually hit.

Tree-SHA512: 1da4088bbda64c5527233de9ec4d03f9e0c1eacddb2ed3deab3cb99eac0293ee6fb846830f97b5e10e230307b6d7fd18013043173aa4f27ef171d9da626e2c88

src/rpc/rawtransaction.cpp

@@ -1032,6 +1032,10 @@ UniValue sendrawtransaction(const JSONRPCRequest& request)
         }
     } else if (fHaveChain) {
         throw JSONRPCError(RPC_TRANSACTION_ALREADY_IN_CHAIN, "transaction already in block chain");
+    } else {
+        // Make sure we don't block forever if re-sending
+        // a transaction already in mempool.
+        promise.set_value();
     }
 
     } // cs_main