LU-15506 tests: fix sha1sum error for disk images with multiple mdts

LU-15506 tests: fix sha1sum error for disk images with multiple mdts

For new disk2_10-ldiskfs and disk2_12-ldiskfs images,
check remote_dir for sha1sum test. For dne image, check
striped_dir.

One minor ost2 replace_nids fix for DNE test images.

Add verbose debug messages to make test flow more clear.

Test-Parameters: trivial testlist=conf-sanity env=ONLY=32 mdscount=1 mdtcount=1
Test-Parameters: testlist=conf-sanity env=ONLY=32 mdscount=2 mdtcount=4
Fixes: f2143c0790bb ("LU-11643 tests: add new images and tests for upgrade")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Wei Liu <sarah@whamcloud.com>
Change-Id: I582bcdbf72d72e6da636559a24b1ecc89553c895
Reviewed-on: https://review.whamcloud.com/46404
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>