LU-16984 tests: replay-dual/31 checks file from DIR2

LU-16984 tests: replay-dual/31 checks file from DIR2

Move replay-dual/test_31 to correct place.
In replay-dual/test_31, check file existence from DIR2.
Add more messages for diagnosis.

Lustre-change: https://review.whamcloud.com/51762
Lustre-commit: TBD (from 025aa6e78ca6d3f4fc872b2b616034ec5b28952a)

Fixes: 07764c4eeb ("LU-16953 tests: wait longer in replay-dual/test_31")
Signed-off-by: Lei Feng <flei@whamcloud.com>
Test-Parameters: trivial testlist=replay-dual env=ONLY=31,ONLY_REPEAT=100
Change-Id: Iee679ee94ac2cb51baad1651bfaddf452fafdbd1
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/51764
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>