NFS: Do not report writeback errors in nfs_getattr()

stable inclusion
from linux-4.19.231
commit d2ba21f271eb167ac2b0581598e55222b89f0f32

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

commit d19e0183 upstream.

The result of the writeback, whether it is an ENOSPC or an EIO, or
anything else, does not inhibit the NFS client from reporting the
correct file timestamps.

Fixes: 79566ef0 ("NFS: Getattr doesn't require data sync semantics")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>