Applied patch from jira issue - OFBIZ-5385 - Purchase order immutable/unchangeable errors when adding variant products.
In this changes Arun has taken care of cloning related concern raised by Adrian. Thanks Arun for the contribution.

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1647946 13f79535-47bb-0310-9956-ffa450edef68