[eCommerce] search box problem and box going narrow

<b>Specification:</b> Bootstrap CSS class to fix this issue.
website_sale module  »  views  » templetes.xml (id="product" template)
  »  Exisiting <code>&lt;div class="row"&gt;..&lt;/div&gt;</code>
       »  Add col-md-12 and center-block class

<b>Task:</b> https://www.odoo.com/web#id=9654&view_type=form&model=project.task&menu_id=3942&action=327
 <b>Pad:</b> https://pad.odoo.com/p/r.bofwElvy1bAQy3sp