doc: fix makeinfo errors and one warning

commit 4afa50b added few lines that are syntactically incorrect
with leading plus sign.

Cc: Denis Ovsienko <infrastation@yandex.ru>
Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
2 files changed