NFSD: Clean up forgetting clients

I added in a generic for-each loop that takes a pass over the client_lru
list for the current net namespace and calls some function.  The next few
patches will update other operations to use this function as well.  A value
of 0 still means "forget everything that is found".

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/netns.h

@@ -92,5 +92,8 @@ struct nfsd_net {
 	time_t nfsd4_grace;
 };
 
+/* Simple check to find out if a given net was properly initialized */
+#define nfsd_netns_ready(nn) ((nn)->sessionid_hashtbl)
+
 extern int nfsd_net_id;
 #endif /* __NFSD_NETNS_H__ */