NFSv4: Fix return value in nfs_finish_open()

[ Upstream commit 9821421a291b548ef4369c6998745baa36ddecd5 ]

If the file turns out to be of the wrong type after opening, we want
to revalidate the path and retry, so return EOPENSTALE rather than
ESTALE.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>