This value controls the channels which will be scanned during
the off-channel scan. Two special values should be noted:
all - causes the radio to scan all channels supported by
the configured country code. While on each channel
the radio will send out probe requests if the value
of extremeWirelessScanSendProbeRequest is true.
every - causes the radio to scan all channels, even those
which are restricted by the country code. The
radio will only send probe request on channels that
are legal for that country code.