According to RFC5661, section 12.5.3. the layout stateid is no longer
valid once the client no longer holds any layout segments. Ensure that
we mark it invalid.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>