t6416, t6422: fix incorrect untracked file count

t6416, t6422: fix incorrect untracked file count

Apparently I don't know how to count untracked files, and since the
tests in question were marked as test_expect_failure, no one ever
noticed it until now.  Correct the count, as these tests clearly create
three untracked files ('out', 'err', and 'file_count').

(I believe this problem arose because earlier incarnations counted lines
via a pipe to 'wc -l'.  Reviewers asked that it be replaced by writing
the output to a file and using test_line_count, but when the temporary
output was added to a separate file, the count of untracked files should
have increased.)

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>