LU-8066 lod: migrate from proc to sysfs

Move the lod module from using proc for most single value files
to sysfs. Create the default attrs for dt_devices which can be
used for other server side devices.

Change-Id: I734f01ef0d9f0c18efc141c835e4cf8ad2365250
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/32198
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Sonia Sharma <sharmaso@whamcloud.com>