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

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

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

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/fs/lustre-release/+/51762
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>