title: Cakephp contain is included in query
body: <p>When I run the following code the Containable behaviour does not work. <strong>I don't want to use a manual join!</strong></p>
  
  <pre><code>$data = $this-&gt;Variant-&gt;find('first', array(
          'contain' =&gt; array('VariantValue'),
          'conditions' =&gt; array(
              'Variant.product_id' =&gt; $product_id
          ),
          'group' =&gt; 'VariantValue.variant_id having count(*) = 2'
  ));
  </code></pre>
  
  <p><strong>Database:</strong></p>
  
  <pre><code>CREATE TABLE `variants` (
     `id` int(11) NOT NULL,
     `product_id` int(11) NOT NULL,
     `price` decimal(7,2) NOT NULL
  )    
  
  CREATE TABLE `variant_values` (
     `id` int(11) NOT NULL,
     `variant_id` int(11) NOT NULL,
     `value_id` int(11) NOT NULL
  )
  </code></pre>
  
  <p><strong>The models:</strong></p>
  
  <pre><code>class Variant extends AppModel {
  
      public $actsAs = array('Containable');
      public $belongsTo = array(
          'Product' =&gt; array(
              'className' =&gt; 'Product',
              'foreignKey' =&gt; 'product_id'
           )
      );
      public $hasMany = array('CartVariant', 'VariantValue');
  }
  
  class VariantValue extends AppModel {
  
      public $actsAs = array('Containable');
      public $belongsTo = array(
          'Value' =&gt; array(
              'className' =&gt; 'Value',
              'foreignKey' =&gt; 'value_id'
          ),
          'Variant' =&gt; array(
              'className' =&gt; 'Variant',
              'foreignKey' =&gt; 'variant_id'
          )
      );
  }
  </code></pre>
  
  <p><strong>The error message:</strong></p>
  
  <p>Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column VariantValue.variant_id in group statement</p>
  
  <p>SQL Query: 
  SELECT Variant.id, Variant.product_id, Variant.price FROM variants AS Variant WHERE Variant.product_id = 1 GROUP BY VariantValue.variant_id having count(*) = 2</p>