title: Woocommerce product query for stock status
body: <p>I use 3 statuses of availability: 'in stock', 'out of stock' and 'allow for backorders'. I want  export products which is only 'in stock' status to XML. The problem is that woocommerce returns value "instock" for both statuses: 'in stock' and 'allow for backorders'.
  Now the query looks like:</p>
  
  <pre><code>$query = array(
      'post_type' =&gt; 'product',
      'posts_per_page' =&gt; -1,
      'meta_query' =&gt; array(
          array(
              'key' =&gt; '_stock_status',
              'value' =&gt; 'instock'
          )
      )
  );
  $wp_query = &amp; new WP_Query($query);
  while ($wp_query-&gt;have_posts()) : $wp_query-&gt;the_post();
  </code></pre>
  
  <p>And it export products with 'instock' and 'backorders_allowed' statuses. Maybe there is the way to exclude products with 'backorders_allowed'.</p>