esc_attr does not double encode

fixes woocommerce#9287

templates/single-product/add-to-cart/variable.php

@@ -9,7 +9,7 @@
  * as little as possible, but it does happen. When this occurs the version of the template file will
  * be bumped and the readme will list any important changes.
  *
- * @see 	    http://docs.woothemes.com/document/template-structure/
+ * @see 	http://docs.woothemes.com/document/template-structure/
  * @author  WooThemes
  * @package WooCommerce/Templates
  * @version 2.5.0
@@ -24,7 +24,7 @@
 
 do_action( 'woocommerce_before_add_to_cart_form' ); ?>
 
-<form class="variations_form cart" method="post" enctype='multipart/form-data' data-product_id="<?php echo absint( $product->id ); ?>" data-product_variations="<?php echo esc_attr( json_encode( $available_variations ) ) ?>">
+<form class="variations_form cart" method="post" enctype='multipart/form-data' data-product_id="<?php echo absint( $product->id ); ?>" data-product_variations="<?php echo htmlspecialchars( json_encode( $available_variations ) ) ?>">
 	<?php do_action( 'woocommerce_before_variations_form' ); ?>
 
 	<?php if ( empty( $available_variations ) && false !== $available_variations ) : ?>