LU-8066 osd: migrate from proc to sysfs

LU-8066 osd: migrate from proc to sysfs

Move the osd based modules, osd-ldiskfs and osd-zfs, from using
proc for most single value files to sysfs. Also update MGS as
well since it had symlinks into the osd proc tree originally.

Change-Id: Ib3838038299937d7e9ae68130d50ec2afb84e996
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/32810
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>