nfsd4: don't allow reclaims of expired clients

nfsd4: don't allow reclaims of expired clients

When a confirmed client expires, we normally also need to expire any
stable storage record which would allow that client to reclaim state on
the next boot.  We forgot to do this in some cases.  (For example, in
destroy_clientid, and in the cases in exchange_id and create_session
that destroy and existing confirmed client.)

But in most other cases, there's really no harm to calling
nfsd4_client_record_remove(), because it is a no-op in the case the
client doesn't have an existing

The single exception is destroying a client on shutdown, when we want to
keep the stable storage records so we can recognize which clients will
be allowed to reclaim when we come back up.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>