Handle multiple external interfaces when MultiWAN is not enabled
Migrated from: https://tracker.clearos.com/view.php?id=2233
Reported by: Peter Baldwin
It is not unusual for an administrator to reconfigure network settings on a new install. In particular, there are times when two (or more) external interfaces are defined without having MultiWAN enabled. This can put the default route in a state of limbo even after getting back to a single external interface. Review.