LU-13366 doc: add SEL options to util's man pages

LU-13366 doc: add SEL options to util's man pages

a couple of documents missed the SEL info:
- lfs man page
- lfs setstripe help message
- lfs find help message

Test-Parameters: trivial
Signed-off-by: Vitaly Fertman <c17818@cray.com>
Change-Id: Ifd4e55877309a29cafdd05d007ace6660d0f775b
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Tested-by: Elena Gryaznova <c17455@cray.com>
Reviewed-on: https://es-gerrit.dev.cray.com/156672
HPE-bug-id: LUS-8149
Reviewed-on: https://review.whamcloud.com/37962
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>