Exponent for WRED calculates the average length of queue.
If 'h3cIfQoSWredGroupType' is 'queue', the object is ineffective.
So, it must use the object, which is 'h3cIfQoSWredGroupExponent' of
h3cIfQoSWredGroupContentTable, to indicate the exponent of
each queue of the queue WRED group.