rgw: cls_user sync entry stats when not a add op

rgw: cls_user sync entry stats when not a add op

when cls_user_set_buckets_info is called by create bucket, we sync the
entry stats from the given info and thus end up setting the existing
stats on a bucket to 0, this is later corrected during a bucket sync,
however there is no need to update the entry and override the existing
bucket count and stats (as these aren't set during the call) and if it
is a new bucket call we already copy over the values earlier.

Fixes: http://tracker.ceph.com/issues/16357
Reported-by: pengju jiao <pj.jiao@139.com>
Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>