test/file-register: fix heap overflow read on test_basic
test/file-register: fix heap overflow read on test_basic

When `test_basic` is called with `fail == 1`, the allocated array for
it is just 10, but the close_files is always called with 100.

Signed-off-by: Ammar Faizi <a8266392a329a5c7b5ab982a8996391d75b6438e@gmail.com>

axboe/liburing,axboe/liburing,axboe/liburing