test: fix nakamoto_attempt_time test

Pause the miner iwhen submitting transactions so that all transactions
intended to be in one block will be in the same block.

Author: obycode

testnet/stacks-node/src/tests/nakamoto_integrations.rs

@@ -6012,6 +6012,10 @@ fn nakamoto_attempt_time() {
                 break account;
             };
 
+            // Stall the miner to make sure it waits until all transactions are
+            // submitted before it mines a block
+            TEST_MINE_STALL.set(true);
+
             let mut sender_nonce = account.nonce;
             for _ in 0..txs_per_block {
                 let transfer_tx = make_stacks_transfer(
@@ -6026,6 +6030,8 @@ fn nakamoto_attempt_time() {
                 submit_tx(&http_origin, &transfer_tx);
             }
 
+            TEST_MINE_STALL.set(false);
+
             // Miner should have made a new block by now
             let wait_start = Instant::now();
             loop {