LU-930 ptlrpc: quiet idle import logging

LU-930 ptlrpc: quiet idle import logging

Don't log a debug message for every idle import every 25s, as this
pushes out other more important messages from the logs.

Fixes: 5a6ceb664f ("LU-7236 ptlrpc: idle connections can disconnect")
Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Id98c2acad07cec62af0d705a437a4d2915ce9f62
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54540
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>