The current state of ccmPhoneExtensionTable. 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
ccmPhoneExtensionTable. 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.