Fix mis-backport of t7002

Fix mis-backport of t7002

The original patch that became cfe370c (grep: do not segfault when -f is
used, 2009-10-16), was made against "maint" or newer branch back then, but
the fix addressed the issue that was present as far as in 1.6.4 series.

The maintainer backported the patch to the 1.6.4 maintenance branch, but
failed to notice that the new tests assumed the setup done by the script
in "maint", which did quite a lot more than the same test script in 1.6.4
series, and the output didn't match the expected result.

This should fix it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>