The value of tmnxL2tpTuCfgAvpHiding specifies
when the H bit in the header of each Attribute Value Pair (AVP)
is set for the L2TP control messages related to this
Layer Two Tunneling Protocol Tunnel.
The value 'default' specifies that the value must be set to the actual
value of the object tmnxL2tpTgCfgAvpHiding of the tunnel group this
tunnel belongs to.