[mempool] only update lockpoints for non-removed entries

Each entry's lockpoints are independent of one another, so there isn't
any reason to update lockpoints for entries that will be removed.
Separating the loops also allows us to move validation logic out and
leave lockpoints in txmempool.

src/txmempool.cpp

@@ -642,7 +642,7 @@ void CTxMemPool::removeForReorg(CChainState& active_chainstate, int flags)
     for (indexed_transaction_set::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
         const CTransaction& tx = it->GetTx();
         LockPoints lp = it->GetLockPoints();
-        bool validLP =  TestLockPointValidity(active_chainstate.m_chain, &lp);
+        const bool validLP = TestLockPointValidity(active_chainstate.m_chain, &lp);
         CCoinsViewMemPool view_mempool(&active_chainstate.CoinsTip(), *this);
         if (!CheckFinalTx(active_chainstate.m_chain.Tip(), tx, flags)
             || !CheckSequenceLocks(active_chainstate.m_chain.Tip(), view_mempool, tx, flags, &lp, validLP)) {
@@ -663,15 +663,19 @@ void CTxMemPool::removeForReorg(CChainState& active_chainstate, int flags)
                 }
             }
         }
-        if (!validLP) {
-            mapTx.modify(it, update_lock_points(lp));
-        }
     }
     setEntries setAllRemoves;
     for (txiter it : txToRemove) {
         CalculateDescendants(it, setAllRemoves);
     }
     RemoveStaged(setAllRemoves, false, MemPoolRemovalReason::REORG);
+    auto chain = active_chainstate.m_chain;
+    for (indexed_transaction_set::const_iterator it = mapTx.begin(); it != mapTx.end(); it++) {
+        LockPoints lp = it->GetLockPoints();
+        if (!TestLockPointValidity(chain, &lp)) {
+            mapTx.modify(it, update_lock_points(lp));
+        }
+    }
 }
 
 void CTxMemPool::removeConflicts(const CTransaction &tx)