torture: Protect kvm-remote.sh directory trees from /tmp reaping

The kvm-remote.sh script places the datestamped directory containing
all the build artifacts in the destination systems' /tmp directories,
where they accumulate runtime artifacts such as console.log. This works,
but some systems have a habit of removing files in /tmp that have not
been recently accessed. This commit therefore runs a simple script that
periodically accesses all files in the datestamped directory.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>