LU-3155 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.

Xyratex-bug-id: MRP-272
Signed-off-by: Artem Blagodarenko <artem_blagodarenko@xyratex.com>
Change-Id: I19ec3f14e339f780ef1403f2902f6baa9e789614
Reviewed-on: http://review.whamcloud.com/6025
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>