This object is used to indicate number of MGCs
to be associated with this MGC Group.
The value zero means there is no MGC in the MGC Group.
When the entry create, this value is set to 0.
Adding/deleting MGC to/from MGC group is through
cMgcGrpTable.
After a MGC added/deleted to/from this MGC group,
the value of this object will be incremented/decremented
by 1.
If the value of this object is zero, it is not allowed to
associate this MGC group with any profile or gateway.