Branch HEAD

b=16887
i=pravin.shelar
i=adilger

Address LBUG, ASSERTION(client_stat->nid_exp_ref_count == 0) failed:count -1
* add client stat on obd_nid_stat after client stat is ready.
* properly decrease exp_nid_stats' nid_exp_ref_count in lprocfs_exp_cleanup().