title: Search form shortcode redirects to shortcode tag istead of ?s
body: <p>I have created a search form for a page and placed it in a function that gets shortcoded. But the issue is that the action of the form goes to the shortcode tag instead of ?s. For example if I do a search it will redirect to</p>
  
  <p><strong><a href="http://www.domain.com/?search-course-provider=course+6&amp;providers=product_cat&amp;post_type=product" rel="nofollow">http://www.domain.com/?search-course-provider=course+6&amp;providers=product_cat&amp;post_type=product</a></strong></p>
  
  <p>instead of </p>
  
  <p><strong><a href="http://www.domain.com/?s=course&amp;providers=product_cat&amp;post_type=product" rel="nofollow">http://www.domain.com/?s=course&amp;providers=product_cat&amp;post_type=product</a></strong></p>
  
  <p><code>?s</code> becomes <code>?search-course-provider</code>. How can I fix this issue.</p>
  
  <pre><code>function search_course_provider() {
  ?&gt;
      &lt;div style="background: #f4f4f4; height: 150px" class="container-fluid"&gt;
          &lt;div  class="container"&gt;
              &lt;form action="&lt;?php echo site_url('/'); ?&gt;" method="get" id="searchform" class="center-block-page"&gt;
                  &lt;input id="search-course-provider" type="text" placeholder="What do you want to study?" name="search-course-provider" value=""&gt;
                  &lt;input type="submit" id="enter" alt="waiting" value=""&gt;
                  &lt;input type="hidden" value="product_cat" name="providers" /&gt;
                  &lt;input type="hidden" value="product" name="post_type" /&gt;
              &lt;/form&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;?php
  }
  add_shortcode('search-course-provider', 'search_course_provider');
  </code></pre>