LU-1749 llog: MDT should work if cancel llog failed with -ESTALE

LU-1749 llog: MDT should work if cancel llog failed with -ESTALE

Cancel catlog may be stale, in this case MDT should continue to work.

Signed-off-by: Lai Siyao <laisiyao@whamcloud.com>
Change-Id: I1934be855f9a1ad8d45750bd7e8330e81a888545
Reviewed-on: http://review.whamcloud.com/4163
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>