If data-port or bridge-mappings are incorrect this should be reflected in workload status

If data-port or bridge-mappings are incorrect, it would be very helpful to report this in workload status.

If data-port is set to an interface name and that is not present it will error out, but if it is set to mac addresses even when there is no match the charm gives no indication there is a problem.

This can lead to very difficult to debug scenarios where some but not all FIPs or virtual router interfaces are not accessible.