The threshold value the route metric MUST reach in order for
the tracked object to transition to the 'up' state from the
'down' state.
This value MUST be less than the value specified in
etsysTrackedObjectsRouteMetricDownThresh. An inconsistentValue
error is returned if the value of a set operation is greater
than or equal to etsysTrackedObjectsRouteMetricDownThresh.
This value only has meaning when etsysTrackedObjectsRouteOption
is 'metric'.