The value of vRtrPimNgAFGenMvpnIntersiteShrd specifies whether to use
inter-site shared C-trees or not.
When the value of vRtrPimNgAFGenMvpnIntersiteShrd is set to 'enabled',
the use of inter-site shared C-trees is enabled. When the value is set
to 'disabled', the use of inter-site shared C-trees is disabled.