title: Authentication plugin 'caching_sha2_password' cannot be loaded in circleci/mysql
body: <p>I've recently encountered problems when testing code in CircleCi 2.
  Parts of our config.yml:</p>
  
  <pre><code>jobs:
    build:
      environment:
      docker:
        ...
        - image: circleci/mysql
        - image: rabbitmq:3-alpine
      working_directory: ~/webapp
  
      steps:
        ...
        - run:
            name: Prepare DB
            command: echo "create database" | mysql --host 127.0.0.1
  </code></pre>
  
  <p>The build fails at <code>Prepare DB</code> with </p>
  
  <p><code>ERROR 2059 (HY000): Authentication plugin 'caching_sha2_password' cannot be loaded: Error loading shared library /usr/lib/mysql/plugin/caching_sha2_password.so: No such file or directory
  Exited with code 1</code></p>
  
  <p>This error only occurred now, and no changes has been made to the circle / mysql setup.</p>
  
  <p>From e.g. <a href="https://stackoverflow.com/a/49944625/2713641">https://stackoverflow.com/a/49944625/2713641</a> it is specified that one can set a <code>--default-authentication-plugin=mysql_native_password</code> flag but not sure if that applies here, or how to apply it in a circle ci setup.</p>