LU-18379 tests: wait for stats to expire in conf-sanity/127

LU-18379 tests: wait for stats to expire in conf-sanity/127

fs stats are not updated immediately on the client,
thus we need to wait.

Test-Parameters: env=ONLY=127,ONLY_REPEAT=20 testlist=conf-sanity
Test-Parameters: env=ONLY=127,ONLY_REPEAT=20 testlist=conf-sanity
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I28cf407f9fe4df1f46af8cd88f50670bb8f0d93f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56726
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>