NFSv4: Fix reboot recovery in copy offload

Copy offload code needs to be hooked into the code for handling
NFS4ERR_BAD_STATEID by ensuring that we set the "stateid" field
in struct nfs4_exception.

Reported-by: Olga Kornievskaia <aglo@umich.edu>
Fixes: 2e72448b

 ("NFS: Add COPY nfs operation")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: stable@vger.kernel.org # v4.7+
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>