Applied fix from trunk for revision: 1589612 
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Automatically removes requirement roles before deleting a requirement: thanks to Nicolas Malin for the patch from OFBIZ-4921



git-svn-id: https://svn.apache.org/repos/asf/ofbiz/branches/release12.04@1589615 13f79535-47bb-0310-9956-ffa450edef68