staging/lustre/mgs: set_param -P option that sets value permanently

set_param and conf_param have different syntaxes. Also conf_param
has unimplemented paths and no wildcarding support.

This patch adds set_param -P option, that replaces the whole
conf_param "direct" proc access with a simple upcall-type mechanism
from the MGC. Option conf_param is saved now for compatibility.

Part of the original Lustre commit changes server code.
The patch only picks up client side change.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3155
Lustre-change: http://review.whamcloud.com/6025


Signed-off-by: Artem Blagodarenko <artem_blagodarenko@xyratex.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Signed-off-by: Peng Tao <bergwolf@gmail.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>