The value of vRtrPimNgAFGenMvpnSpmsiAutoDisc specifies if
auto-discovery-disable via BGP is disabled.
When the value of vRtrPimNgAFGenMvpnSpmsiAutoDisc is set to 'true',
then C-trees to P-tunnels binding auto-discovery via BGP is disabled
and it is signaled using PIM join TLVs.