The tmnxEthTunnelMgmtMemberIfIndex indicates the
tmnxEthTunnelMemberIfIndex of the Ethernet Tunnel Group member with
which the Ethernet Tunnel Group port (tmnxEthTunnelIfIndex) inherits
its port configurations.
The management member is set to the first member added to the Ethernet
Tunnel or the next higher member in the case of removing the first
member from the group. If no members are configured for the group, the
tmnxEthTunnelMgmtMemberIfIndex is set to zero (0).