Remove hard coded leading slash in head_tag.cs for DevSite image_path meta tag.

  <meta name="page_type" value="article" /><?cs

      /if ?><?cs

      if:page.image ?>

  <meta name="image_path" value='/<?cs var:page.image ?>' /><?cs

  <meta name="image_path" value='<?cs var:page.image ?>' /><?cs

      /if ?><?cs

/if ?><?cs # END if/else devsite ?><?cs