test: do not rely on US English tracking-info messages
When v1.7.9.2~28^2 (2012-02-02) marked "Your branch is behind" and
friends for translation, it forgot to adjust tests not to check those
messages when tests are being run with git configured to write its
output in another language.
With this patch applied, t2020 and t6040 pass again with
GETTEXT_POISON=YesPlease.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Explained-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>