sudo fails to validate users defined in sudoers Runas_list in RHEL5.5

Issue

• When specifying a Runas_List for both user and group in the sudoers file, the run as user provided with -u <user> command line argument is not validated against the user Runas_List if the group specified is valid
• According to the sudo man page, a combination of valid elements from both lists should be required.