LU-2673 procfs: call lprocfs_free_xxx_stats() later

Defer calls to lprocfs_free_{obd,md}_stats() and
lprocfs_job_stats_fini() until after the corresponding proc entries
have been removed. Change the return of some proc fini()s to void.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Ic410a4cf12eeb084270f5e679222c54b12d80266
Reviewed-on: http://review.whamcloud.com/5160


Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>