fix for IDENTITY-918 by chamath

git-svn-id: https://svn.wso2.org/repos/wso2/carbon/kernel/trunk@179505 a5903396-d722-0410-b921-86c7d4935375
fix to validate role exist before it is excute

git-svn-id: https://svn.wso2.org/repos/wso2/carbon/kernel/trunk@179506 a5903396-d722-0410-b921-86c7d4935375