tests: unset COLUMNS inherited from environment
tests: unset COLUMNS inherited from environment

$COLUMNS must be unset to not interfere with the tests. The tests
already ignore the terminal size because output is redirected to a
file, but COLUMNS overrides terminal size detection and changes the
test output away from the standard 80.

Reported-by: Jeff King <696e3fbcf235d40b6ea1ebd61c87cbea79d444e7@peff.net>
Signed-off-by: Zbigniew Jędrzejewski-Szmek <1a002461b1932d3892b64879e6e8987274fa7074@in.waw.pl>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git