Fix products Facebook og:url meta to return correct url

I've fixed Facebook SEO service for `og:url` to render correct product URL.

Before:
`<meta property="og:url" content="http://demo.sonata-project.org" />`

After:
`<meta property="og:url" content="http://demo.sonata-project.org/shop/product/php-plush-blue/1" />`