LU-2119 osd: missing osd_shutdown()

LU-2119 osd: missing osd_shutdown()

For zfs osd, osd_shutdown() should be called in osd_device_fini()
just like ldiskfs osd does, to can make sure that everything is
cleared even if the osd_process_config(CLEANUP) has no chance to
be called. (when OFD/MDT wasn't started)

Signed-off-by: Niu Yawei <niu@whamcloud.com>
Change-Id: I54f08ac657e01ffb7a367278810016b585b3c0da
Reviewed-on: http://review.whamcloud.com/4239
Tested-by: Hudson
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Mike Pershin <tappro@whamcloud.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>