fix wrong value of op_w_latency perf counter

Fixes: #9217

Signed-off-by: xinxin shu <xinxin.shu@intel.com>
don't update op_rw_rlatency/op_w_rlatency when rlatency is zero

Signed-off-by: xinxin shu <xinxin.shu@intel.com>
Merge pull request #2325 from xinxinsh/wip-9217

fix wrong value of op_w_latency perf counter

Reviewed-by: Sage Weil <sage@redhat.com>