bgpd: add vty command to enable bfd control-plane-check-failure
new vty command is added:
neighbor XXX bfd check-control-plane-failure
this command will enforce the check of bgp controlplane, when bfd
detects changes in the dataplane.
- at configuration, the cbit will be set if that command is executed
- at flapping time, if the command is configured and remote cbit is set
accordingly, then the bfd event will be ignored.
Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>