This object specifies the type of service instance to be used
by the Auto-Ethernet-CFM operation.
When this object is set to value 'vlan', ipslaEthernetGrpCtrlVLAN
must be set, and the value of ipslaEthernetGrpCtrlVLAN will be
used by the Auto-Ethernet-CFM to discover the participating MEPs.
When this object is set to value 'evc', ipslaEthernetGrpCtrlEVC
must be set, and the value of ipslaEthernetGrpCtrlEVC will be
used by the Auto-Ethernet-CFM to discover the participating MEPs.