Enable table doesn't balance out replicas evenly if the replicas were unassigned earlier

Enable table doesn't assign out replicas keeping availability in mind, if the replicas were unassigned before the table was disabled. For example, when a snapshot is restored and then the table is enabled, the replicas are unevenly assigned. The reason for this is that the the enable table invokes randomAssign that assigns one region at a time. Since the master doesn't have any information about the unassigned replicas, the calls to randomAssign can't do any availability checks.