NFS: Fix dentry revalidation on NFSv4 lookup

NFS: Fix dentry revalidation on NFSv4 lookup

commit be189f7e7f03de35887e5a85ddcf39b91b5d7fc1 upstream.

We need to ensure that inode and dentry revalidation occurs correctly
on reopen of a file that is already open. Currently, we can end up
not revalidating either in the case of NFSv4.0, due to the 'cached open'
path.
Let's fix that by ensuring that we only do cached open for the special
cases of open recovery and delegation return.

Reported-by: Stan Hu <stanhu@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Qian Lu <luqia@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>