title: Problems with multiple update in MongoDb
body: <p>I have mongo structure like this:</p>
  
  <pre><code>{
          "_id" : ObjectId("51596b7e469b9c3816000001"),
          "company" : {
                  "_id" : "ade2fd0ec9b8b5e9152e0155",
                  "title" : "LO3426546457"
          },
  }
  {
          "_id" : ObjectId("51596cef469b9c3816000008"),
          "company" : {
                  "_id" : "ade2fd0ec9b8b5e9152e0155",
                  "title" : "LO3426546457"
          },
  }
  {
          "_id" : ObjectId("51596cc3469b9c3816000007"),
          "company" : {
                  "_id" : "ade2fd0ec9b8b5e9152e0155",
                  "title" : "LO3426546457"
          }        
  }
  </code></pre>
  
  <p>And I want to change all 'title' fields for objects with a specific '_id'.
  I do like this:</p>
  
  <pre><code>Collections.UsersCollection.update({
      'company._id': 'ade2fd0ec9b8b5e9152e0155'
  }, {
      $set: {
          'company': { _id: 'ade2fd0ec9b8b5e9152e0155', title: 'blablabla' }
          // I also tried: 'company.title': 'blablabla'
      }
  }, false, true);
  </code></pre>
  
  <p>And after execution that code in Node.js (I use node-mongodb-native), mongo updates <strong>only one</strong> document.</p>
  
  <p>But if I do that command at Mongo Shell (mongo.exe), everything works fine and updates all documents.</p>
  
  <p>What's the problem?</p>