Change GetPriority calculation.

Compute the value of inputs that already are in the chain at time of mempool entry and only increase priority due to aging for those inputs.  This effectively changes the CTxMemPoolEntry's GetPriority calculation from an upper bound to a lower bound.

src/test/policyestimator_tests.cpp

@@ -196,7 +196,7 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
 
     // Test that if the mempool is limited, estimateSmartFee won't return a value below the mempool min fee
     // and that estimateSmartPriority returns essentially an infinite value
-    mpool.addUnchecked(tx.GetHash(),  CTxMemPoolEntry(tx, feeV[0][5], GetTime(), priV[1][5], blocknum, mpool.HasNoInputsOf(tx)));
+    mpool.addUnchecked(tx.GetHash(),  entry.Fee(feeV[0][5]).Time(GetTime()).Priority(priV[1][5]).Height(blocknum).FromTx(tx, &mpool));
     // evict that transaction which should set a mempool min fee of minRelayTxFee + feeV[0][5]
     mpool.TrimToSize(1);
     BOOST_CHECK(mpool.GetMinFee(1).GetFeePerK() > feeV[0][5]);