An entry describes the change in the state of an alarm
condition observed by the device.
The device creates a row in the cfmAlarmHistoryTable when it
observes a change in the state of an alarm condition.
The device destroys a row in the cfmAlarmHistoryTable when it
needs to create a new row, but the number of rows contained by
the cfmAlarmHistoryTable is equal to the value of
cfmAlarmHistorySize.