NFSv3: use nfs_add_or_obtain() to create and reference inodes

mainline inclusion
from mainline-v5.4-rc1
commit 17fd6e45
category: bugfix
bugzilla: NA
CVE: NA

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Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>