LU-7593 target: umount vs tgt_last_rcvd_update deadlock

LU-7593 target: umount vs tgt_last_rcvd_update deadlock

tgt_client_del() and
ofd_commitrw_write->tgt_last_rcvd_update
take transaction and ted->ted_lcd_lock
in different order:

thread1:
    osd_trans_start
    tgt_client_data_update
    tgt_client_del       <<< mutex_lock(&ted->ted_lcd_lock);
    ofd_obd_disconnect
    class_disconnect_export_list
    class_disconnect_exports
    class_cleanup
    ...
    sys_umount

thread2:
    __mutex_lock_slowpath
    mutex_lock          <<< mutex_lock(&ted->ted_lcd_lock);
    tgt_last_rcvd_update
    tgt_txn_stop_cb
    dt_txn_hook_stop
    osd_trans_stop
    ofd_trans_stop
    ofd_commitrw_write
    ...
    tgt_brw_write

Lock only around tgt_client_data_write() inside
the tgt_client_data_update()

Change-Id: Id3f60636be2abb3b70a99ee44b735aab7dfb7657
Seagate-bug-id: MRP-3109
Signed-off-by: Andriy Skulysh <andriy.skulysh@seagate.com>
Reviewed-on: http://review.whamcloud.com/17704
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>