In the Original article the PATH of the properties file (in th value) is not mentioned which will cause the validation to fail:
<module-option name="usersProperties" value="users.properties"/>
<module-option name="rolesProperties" value="roles.properties"/>
It worked for me after adding the location of these propertieds files as following:
<module-option name="usersProperties" value="${jboss.server.config.dir}/users.properties"/>
<module-option name="rolesProperties" value="${jboss.server.config.dir}/roles.properties"/>