Hiding SLA details on Issue Viewing Screen

Following up from JSD-215

Customer would also like to hide SLA from the issue view. The feature from JSD-215 restricts customer to the customer portal but still at times, the usage needs further participation (resolving issue, perform some other workflow transition) and showing the SLA to the customer does not seems fit. They would prefer to have the SLA clocks rendered for certain role or groups so that this information would not be available to be viewed by customer.