NFS: Replace various occurrences of kstrndup() with kmemdup_nul()

When we already know the string length, it is more efficient to
use kmemdup_nul().
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
[Anna - Changes to super.c were already made during fscontext conversion]
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/dns_resolve.c

@@ -93,7 +93,7 @@ static void nfs_dns_ent_init(struct cache_head *cnew,
 	key = container_of(ckey, struct nfs_dns_ent, h);
 
 	kfree(new->hostname);
-	new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
+	new->hostname = kmemdup_nul(key->hostname, key->namelen, GFP_KERNEL);
 	if (new->hostname) {
 		new->namelen = key->namelen;
 		nfs_dns_ent_update(cnew, ckey);

fs/nfs/nfs4namespace.c

@@ -501,7 +501,7 @@ static int nfs4_try_replacing_one_location(struct nfs_server *server,
 		rpc_set_port(sap, NFS_PORT);
 
 		error = -ENOMEM;
-		hostname = kstrndup(buf->data, buf->len, GFP_KERNEL);
+		hostname = kmemdup_nul(buf->data, buf->len, GFP_KERNEL);
 		if (hostname == NULL)
 			break;