LU-2057 ofd: implement jobstats and few fixes

LU-2057 ofd: implement jobstats and few fixes

- implement jobstats for OFD like in obdfilter
- fix ofd_health_check to ignore external lu_env and use local one
  always, because obd_proc_read_health uses it without env
- do object sync only if its version is not yet committed

Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: Idf74ef280f9d71e3db6b45cfacb2f5303b302a77
Reviewed-on: http://review.whamcloud.com/4143
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>