title: Use of positional with two queried arrays, with one not needing to affect positional operator
body: <p>I am trying to push a comment to my <code>Class</code> document collection, which has a list of <code>lessons</code>. I want to make sure that the user posting the comment is registered to the <code>Class</code> and to do that I have a field <code>mentors.mentorList</code> that holds the users that have privilege to post in the <code>Class</code>.</p>
  
  <pre><code>     Class.findOneAndUpdate(
          {_id: "5e1baeb07fcee8639cbce2ac", "mentors.mentorList":{ $eq: "5c9ba636347bb645e0865283" } , 
           "lessons._id": "5db221be211d7b68ac8be618" },
          { $push: { "lessons.$.comments": commentObj } },
          { new: true }
        )
  </code></pre>
  
  <p>Which actually is using the matched index in the <code>mentor.mentorList</code> of the query (index 0) and updating the <code>$push</code> to the <code>lessons[0].comments</code>. Is it possible to exclude the <code>mentors.mentorList</code> from affecting the positional operator?</p>