Load credential when local invocation with docker

[frozenbonito]

What did you implement

Closes #7343

How can we verify it

1. create SSM paramter named test in us-east-1 region

2. create serverless.yml

service: sls-test

provider:
  name: aws
  runtime: nodejs12.x

functions:
  hello:
    handler: handler.hello

3. create handler.js

"use strict";

const AWS = require("aws-sdk");

module.exports.hello = async event => {
  const ssm = new AWS.SSM();
  console.log(await ssm.getParameter({ Name: "test" }).promise());
};

4. run sls invoke local -f hello --docker

Todos

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Is this ready for review?: YES
Is it a breaking change?: NO

[medikoo]

Thanks @frozenbonito looks great!