`AWS_MAX_ATTEMPTS` has no effect with v2

Confirm by changing [ ] to [x] below to ensure that it's a bug:
- [x] I've gone though the [User Guide](https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-welcome.html) and the [API reference](https://docs.aws.amazon.com/cli/latest/reference/)
- [x] I've searched for [previous similar issues](https://github.com/aws/aws-cli/issues) and didn't find any solution

**Describe the bug**

With the v2 CLI, the `AWS_MAX_ATTEMPTS` environment variable does not change the number of max attempts. The variable is documented to work: . It does work with the v1 CLI.

**SDK version number**

aws-cli/2.0.46 Python/3.8.5 Linux/5.4.69 source/x86_64.nixos.20

**Platform/OS/Hardware/Device**

NixOS 20.09

**To Reproduce (observed behavior)**

1. Start an S3 upload like `AWS_MAX_ATTEMPTS=10000 aws s3 cp --debug /tmp/randfile s3://my-bucket/test`
2. Disable networking
3. After about 5 minutes, observe "botocore.retries.standard - DEBUG - Retry needed but retry quota reached, not retrying request."

**Expected behavior**

Upload should continue to retry until `AWS_MAX_ATTEMPTS` attempts are made.

**Logs/output**

[aws-s3-cp.log](https://github.com/aws/aws-cli/files/5405259/aws-s3-cp.log) for `AWS_MAX_ATTEMPTS=10000 aws s3 cp --debug /tmp/randfile s3://my-bucket/test > aws-s3-cp.log 2>&1`.
See "To Reproduce" for the relevant entry.

首先重現文件中記載的 AWS_MAX_ATTEMPTS=10000 命令，並檢視隨附的 aws-s3-cp.log，尤其是 retry-quota 訊息。比較 v2 的行為與所述的 v1 行為及連結的設定文件。當 v2 的 S3 上傳遵循已設定的最大嘗試次數時，即表示完成。

由索引模型根據 Issue 內容生成。