LU-13404 utils: fix lfs mirror duplicate file check

LU-13404 utils: fix lfs mirror duplicate file check

Fix the check_same_file() check to work if the output file does not
exist.  Since the file is opened with O_CREAT|O_EXCL then definitely
it cannot be the same as the input file.

Add test_0j to verify "lfs mirror read -o" and "lfs mirror write -i".

Test-Parameters: trivial testlist=sanity-flr env=ONLY=0j
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ide929b53a528bd0cc77e1f997d3c561c67729179
Reviewed-on: https://review.whamcloud.com/38108
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-by: Oleg Drokin <green@whamcloud.com>