The current state of ccmCTIDeviceDirNumTable. The initial
value of this object is 0 and it will be incremented every time
when there is a change (addition/deletion/modification) to the
ccmCTIDeviceDirNumTable. This value and ccmCallManagerStartTime
should be used together to find if the table has changed or not.
When the call manager is restarted, this will be reset to 0.