cfgtool: Improve link status display

Totemknet is enhanced to use 'n' character for localhost and not adding
status, because it is safe to expect that localhost link is always
connectd. corosync-cfgtool is enhanced to properly decode 'n', '?' and
'd' characters and display its meaning for extended status. Special
characters are also documented in man page.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>