tcp_metrics: do not create an entry from tcp_init_metrics()

tcp_init_metrics() only wants to get metrics if they were
previously stored in the cache. Creating an entry is adding
useless costs, especially when tcp_no_metrics_save is set.

Fixes: 51c5d0c4 ("tcp: Maintain dynamic metrics in local cache.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/ipv4/tcp_metrics.c

@@ -478,7 +478,7 @@ void tcp_init_metrics(struct sock *sk)
 		goto reset;
 
 	rcu_read_lock();
-	tm = tcp_get_metrics(sk, dst, true);
+	tm = tcp_get_metrics(sk, dst, false);
 	if (!tm) {
 		rcu_read_unlock();
 		goto reset;