NFS/pNFS: Fix a leak of the layout 'plh_outstanding' counter

stable inclusion
from linux-4.19.169
commit b2f9fbbc3fa20f066e20f1d676175e4af0e177ba

--------------------------------

commit cb2856c5 upstream.

If we exit _lgopen_prepare_attached() without setting a layout, we will
currently leak the plh_outstanding counter.

Fixes: 411ae722 ("pNFS: Wait for stale layoutget calls to complete in pnfs_update_layout()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>