NFSv4: Move error handling out of the delegation generic code

The NFSv4 delegation recovery code is required by the protocol to handle
more errors. Rather than add NFSv4.0 specific errors into 'generic'
delegation code, we should move the error handling into the NFSv4 layer.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>