fixed duplicate product not having role pricing or tiered pricing

git-svn-id: https://plugins.svn.wordpress.org/wp-easycart/trunk@855924 b8457f37-d9ea-0310-8a92-e5e31aec5664
Committing version 2.0.21, check the change log for more info.

git-svn-id: https://plugins.svn.wordpress.org/wp-easycart/trunk@856006 b8457f37-d9ea-0310-8a92-e5e31aec5664
Committing version 2.0.22, check the change log for more info.

git-svn-id: https://plugins.svn.wordpress.org/wp-easycart/trunk@856841 b8457f37-d9ea-0310-8a92-e5e31aec5664