message: test: Fix race in mempool_accept
diff: @@ -58,6 +58,7 @@ class MempoolAcceptanceTest(BitcoinTestFramework):
  self.mempool_size = 0
  wait_until(lambda: node.getblockcount() == 200)
  assert_equal(node.getmempoolinfo()['size'], self.mempool_size)
  + coins = node.listunspent()
  self.log.info('Should not accept garbage to testmempoolaccept')
  assert_raises_rpc_error(-3, 'Expected type array, got string', lambda: node.testmempoolaccept(rawtxs='ff00baar'))
  @@ -65,7 +66,7 @@ class MempoolAcceptanceTest(BitcoinTestFramework):
  assert_raises_rpc_error(-22, 'TX decode failed', lambda: node.testmempoolaccept(rawtxs=['ff00baar']))
  self.log.info('A transaction already in the blockchain')
  - coin = node.listunspent()[0] # Pick a random coin(base) to spend
  + coin = coins.pop() # Pick a random coin(base) to spend
  raw_tx_in_block = node.signrawtransactionwithwallet(node.createrawtransaction(
  inputs=[{'txid': coin['txid'], 'vout': coin['vout']}],
  outputs=[{node.getnewaddress(): 0.3}, {node.getnewaddress(): 49}],
  @@ -93,7 +94,7 @@ class MempoolAcceptanceTest(BitcoinTestFramework):
  )
  self.log.info('A final transaction not in the mempool')
  - coin = node.listunspent()[0] # Pick a random coin(base) to spend
  + coin = coins.pop() # Pick a random coin(base) to spend
  raw_tx_final = node.signrawtransactionwithwallet(node.createrawtransaction(
  inputs=[{'txid': coin['txid'], 'vout': coin['vout'], "sequence": 0xffffffff}], # SEQUENCE_FINAL
  outputs=[{node.getnewaddress(): 0.025}],
  