NFSv4.1/pnfs: Ensure we handle delegation errors in nfs4_proc_layoutget()

nfs4_handle_exception() relies on the caller setting the 'inode' field
in the struct nfs4_exception argument when the error applies to a
delegation.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>