test: fix for COLUMNS and bash 5

test: fix for COLUMNS and bash 5

Since c49a177bec (test-lib.sh: set COLUMNS=80 for --verbose
repeatability, 2021-06-29) multiple tests have been failing when using
bash 5 because checkwinsize is enabled by default, therefore COLUMNS is
reset using TIOCGWINSZ even for non-interactive shells.

It's debatable whether or not bash should even be doing that, but for
now we can avoid this undesirable behavior by disabling this option.

Reported-by: Fabian Stelzer <fabian.stelzer@campoint.net>
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
[jc: with SZEDER Gábor's suggestion to do this before setting COLUMNS]
Signed-off-by: Junio C Hamano <gitster@pobox.com>