Bugfix: ancestor modifed fees were incorrect for descendants

If prioritisetransaction was called for a tx with in-mempool
descendants, the modified ancestor fee values for those descendants was
incorrect.

src/txmempool.cpp

@@ -912,6 +912,13 @@ void CTxMemPool::PrioritiseTransaction(const uint256& hash, const CAmount& nFeeD
             BOOST_FOREACH(txiter ancestorIt, setAncestors) {
                 mapTx.modify(ancestorIt, update_descendant_state(0, nFeeDelta, 0));
             }
+            // Now update all descendants' modified fees with ancestors
+            setEntries setDescendants;
+            CalculateDescendants(it, setDescendants);
+            setDescendants.erase(it);
+            BOOST_FOREACH(txiter descendantIt, setDescendants) {
+                mapTx.modify(descendantIt, update_ancestor_state(0, nFeeDelta, 0, 0));
+            }
         }
     }
     LogPrintf("PrioritiseTransaction: %s feerate += %s\n", hash.ToString(), FormatMoney(nFeeDelta));