LU-14736 utils: Change leak_finder to use stdout

LU-14736 utils: Change leak_finder to use stdout

It is not an error for a leak checking script to find a
leak, so don't have leak_finder.pl print to stderr.  It also
prints several pieces of basic status to stderr, for which
there is no reason at all.

This makes it easier to redirect the output for interactive
use.

Signed-off-by: Patrick Farrell <farr0186@gmail.com>
Change-Id: Iab226726ca4b36ada40a305962beedc363398c37
Reviewed-on: https://review.whamcloud.com/43934
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Aurelien Degremont <degremoa@amazon.com>