If the cnpdTopNConfigStatsSelect is
bitRateIn, bitRateOut or bitRateSum, then
this value is the interval in seconds that
the bitrate is sampled.
This has no effect if the cnpdTopNConfigStatsSelect
is byte or packet based.
When this object is modified by the management
station, a new sample period is started regardless
of whether the original cnpdTopNConfigSampleTime
was finished.