使用hardhat自动化部署合约的时候，在创建合约时出现SafeERC20: approve from non-zero to non-zero allowance问题：

部署脚本如下：

import { ethers, network } from "hardhat";
import { Signer, BigNumber, utils } from "ethers";

const MaxUint256 = BigNumber.from(2).pow(256).sub(1);

async function main() {
  let gov: Signer;
  [gov] = await ethers.getSigners();
  console.log(`gov address: ${await gov.getAddress()}`);

  let mdexRouter;
  let hecoPool;
  // mocks
  if (network.name == 'heco_mainnet') {
    // todo

  } else if (network.name == 'bsc_testnet') {
    // tokens
    const Token = await ethers.getContractFactory("TestToken");
    const bnb = await Token.attach('0xc2fd8B9D7eb1bc91d68803a08691FfE2ed8c3ddc');
    const cake = await Token.attach('0x24b7b032e73B939ff94F0225b0908a38a9B2130B');
    const wbnb = await Token.attach('0x5F68D16D2ee5A40f4294185536d103EfEfD8f934');

    const MdexRouterMock = await ethers.getContractFactory("MdexRouterMock");
    mdexRouter = await MdexRouterMock.attach('0x56f390BB3feB639C274e1cd9F4EEFf0F2e969C01');

    const HecoPoolMock = await ethers.getContractFactory("HecoPoolMock");
    hecoPool = await HecoPoolMock.deploy(cake.address);
    await hecoPool.add('0x12F2Cf3CAf5F17F8645A10fD5bF014fA7138D32C');
    const pid = await hecoPool.LpOfPid('0x12F2Cf3CAf5F17F8645A10fD5bF014fA7138D32C');
    await cake.connect(gov).transfer(hecoPool.address, utils.parseEther('10000000'));

    // vault
    const Vault = await ethers.getContractFactory("VolcanoVault");
    const vault = await Vault.deploy();

    const rewards = await gov.getAddress();
    await vault.initialize('0x12F2Cf3CAf5F17F8645A10fD5bF014fA7138D32C', await gov.getAddress(), rewards, await gov.getAddress(), await gov.getAddress());
    await vault.connect(gov).setDepositLimit(MaxUint256);

    const StrategyPancakeCAKELP = await ethers.getContractFactory("StrategyPancakeCAKELP");
    const strategyPancakeCAKELP = await StrategyPancakeCAKELP.deploy(vault.address, pid, hecoPool.address, mdexRouter.address, wbnb.address, cake.address, {gasLimit:10000000});
    await vault.addStrategy(strategyPancakeCAKELP.address, 10000, 0, MaxUint256, 1000); 

    console.log(`Contract Deployed Summary\n=========================`);
    console.log(`|  BNB  |  ${bnb.address}  |`);
    console.log(`|  CAKE  |  ${cake.address}  |`);
    console.log(`|  WBNB  |  ${wbnb.address}  |`);

    console.log(`|  MdexRouter  |  ${mdexRouter.address}  |`);
    console.log(`|  HecoPool  |  ${hecoPool.address}  |`);

    console.log(`|  Vault  |  ${vault.address}  |`);
    console.log(`|  StrategyPancakeCAKELP  |  ${strategyPancakeCAKELP.address}  |`);
  }

}

// We recommend this pattern to be able to use async/await everywhere
// and properly handle errors.
main()
  .then(() => process.exit(0))
  .catch(error => {
    console.error(error);
    process.exit(1);
  });