LU-16526 lmv: module params for default dir layout

LU-16526 lmv: module params for default dir layout

add module parameters to let the default ROOT layout to be flexible
enough to be disabled now and set to something arbitrary in future.

HPE-bug-id: LUS-11140
Signed-off-by: Vitaly Fertman <c17818@cray.com>
Change-Id: I66cae2e0aa5be9c56552bcf0e8810f3f1b944836
Reviewed-on: https://es-gerrit.dev.cray.com/161058
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49878
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>