qa: use prev height as nLockTime for coinbase txs created in unit tests

We don't set the nSequence as it will be set directly in the block template generator in a following
commit.

Author: darosior

src/test/blockfilter_index_tests.cpp

@@ -81,6 +81,7 @@ CBlock BuildChainTestingSetup::CreateBlock(const CBlockIndex* prev,
     }
     {
         CMutableTransaction tx_coinbase{*block.vtx.at(0)};
+        tx_coinbase.nLockTime = static_cast<uint32_t>(prev->nHeight);
         tx_coinbase.vin.at(0).scriptSig = CScript{} << prev->nHeight + 1;
         block.vtx.at(0) = MakeTransactionRef(std::move(tx_coinbase));
         block.hashMerkleRoot = BlockMerkleRoot(block);

src/test/validation_block_tests.cpp

@@ -82,7 +82,9 @@ std::shared_ptr<CBlock> MinerTestingSetup::Block(const uint256& prev_hash)
     txCoinbase.vout[0].nValue = 0;
     txCoinbase.vin[0].scriptWitness.SetNull();
     // Always pad with OP_0 at the end to avoid bad-cb-length error
-    txCoinbase.vin[0].scriptSig = CScript{} << WITH_LOCK(::cs_main, return m_node.chainman->m_blockman.LookupBlockIndex(prev_hash)->nHeight + 1) << OP_0;
+    const int prev_height{WITH_LOCK(::cs_main, return m_node.chainman->m_blockman.LookupBlockIndex(prev_hash)->nHeight)};
+    txCoinbase.vin[0].scriptSig = CScript{} << prev_height + 1 << OP_0;
+    txCoinbase.nLockTime = static_cast<uint32_t>(prev_height);
     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
 
     return pblock;