title: typeorm: force mysql2 if mysql is installed
body: <p>I know this is a special use case, but I have both <code>mysql</code> and <code>mysql2</code> packages installed and I need to test both of them.
  However as my understanding typeorm will first check if <code>mysql</code> is in the <code>node_modules</code> and use it.</p>
  <p>How can I force <code>mysql2</code> to be used instead? Or programmatically switch between them?
  Thanks</p>