NFS: Don't report ENOSPC write errors twice

Any errors reported by the write() system call need to be cleared from
the file descriptor's error tracking. The current call to nfs_wb_all()
causes the error to be reported, but since it doesn't call
file_check_and_advance_wb_err(), we can end up reporting the same error
a second time when the application calls fsync().

Note that since Linux 4.13, the rule is that EIO may be reported for
write(), but it must be reported by a subsequent fsync(), so let's just
drop reporting it in write.

The check for nfs_ctx_key_to_expire() is just a duplicate to the one
already in nfs_write_end(), so let's drop that too.

Reported-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Fixes: ce368536 ("nfs: nfs_file_write() should check for writeback errors")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>