checkMultipleTimeInstances doesn't work for EL extensions

To guard against specifying multiple instances in instance tag, CoordSubmitXCommand.checkMultipleTimeInstances checks for ',' in instance tag. This breaks for EL extensions. We have EL extension today(0,0) which maps to start day of nominal time. today(0,0) resolves to a single instance and presence of ',' doesn't imply that it resolves to multiple instances

Can you please fix this