Fix race condition in test for *FileID functions

Fix race condition in test for *FileID functions

In this test the “file ID” of a temporary file is compared against the
file ID gathered via an open file descriptor to the same file. For
reasons unknown to me utime(2) is called in-between to update the
inode's a- and mtime. Depending on the file system's timestamp
resolution this can lead to a different file ID.

Found by chance during QA and reproduced by adding a delay before the
call to utime(2).

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>