LU-3496 ost: lprocfs batch update

LU-3496 ost: lprocfs batch update

Update lprocfs stats such as cache hits, misses, totals
using single calls to lprocfs_counter_add so as to
improve performance.

Non-zero number of hits/misses/totals for a single RPC
counts as a single sample for the respective hits/misses/totals
counter.

Signed-off-by: Andrew Perepechko <andrew_perepechko@xyratex.com>
Reviewed-by: Alexander Boyko <Alexander_Boyko@xyratex.com>
Reviewed-by: alexander_zarochentsev@xyratex.com
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>
Xyratex-bug-id: MRP-999
Change-Id: I8771e81b7e0356436a1ffcb7e9c51b87580750a9
Reviewed-on: http://review.whamcloud.com/6756
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>