message: [faucet] return expected DD next sequence number
  Closes:
  Approved by: davidiw
diff: @@ -64,15 +64,20 @@ def send_transaction():
  try:
  create_client()
  + application.client.sendline("q as 000000000000000000000000000000dd")
  + application.client.expect(r"sequence_number: ([0-9]+)", timeout=1)
  + if application.client.match:
  + next_dd_seq = int(application.client.match.groups()[0]) + 1
  + else:
  + return 'DD sequence number not found', 400
  +
  application.client.sendline(
  "a m {} {} {} use_base_units".format(auth_key, amount, currency_code))
  application.client.expect("Mint request submitted", timeout=2)
  - application.client.sendline("q as 000000000000000000000000000000dd")
  - application.client.expect(r"sequence_number: ([0-9]+)", timeout=1)
  application.client.terminate(True)
  except pexpect.exceptions.ExceptionPexpect:
  application.client.terminate(True)
  raise
  - return application.client.match.groups()[0]
  + return str(next_dd_seq)
  