IPv6 support for IS-IS BFD

You can configure IS-IS BFD sessions for IPv6. You can enable IS-IS BFD sessions by including the bfd-liveness-detection statement at the [edit protocols isis interface interface-name family inet|inet6] hierarchy level. Currently, IS-IS BFD configuration is available at the [edit protocols isis interface interface-name] hierarchy level. At present, BFD configuration is supported at both of these hierarchy levels.