Discount dial errors that won't affect connection tracking

This will reduce pressure on the conntrack instance.

client.go

@@ -530,7 +530,11 @@ func (cl *Client) dialFirst(ctx context.Context, addr string) dialResult {
 					countDialResult(err)
 					dr := dialResult{c, network}
 					if c == nil {
-						cte.Done()
+						if err != nil && forgettableDialError(err) {
+							cte.Forget()
+						} else {
+							cte.Done()
+						}
 					} else {
 						dr.Conn = closeWrapper{c, func() error {
 							err := c.Close()
@@ -567,6 +571,10 @@ func (cl *Client) dialFirst(ctx context.Context, addr string) dialResult {
 	return res
 }
 
+func forgettableDialError(err error) bool {
+	return strings.Contains(err.Error(), "no suitable address found")
+}
+
 func (cl *Client) noLongerHalfOpen(t *Torrent, addr string) {
 	if _, ok := t.halfOpen[addr]; !ok {
 		panic("invariant broken")