The value of tmnxVrrpPortDownEventType specifies whether this
event is a 'delta' or an 'explicit' event. When the event is
'set', the value of tmnxVrrpPortDownEventPriority will be
subtracted from the in-use priority in case of a 'delta' event
or the in-use priority will be explicitly overridden by the
value of tmnxVrrpPortDownEventPriority in case of an 'explicit'
event.