Id check tests: stop using Exchange (#1343)

Using Exchange doesn't add anything, as it just wraps client.Exchange
with a default client.

Remove them and speed up the tests, goes from 3s to 1s (for the entire
test suite).

Signed-off-by: Miek Gieben <[email protected]>

Author: miekg

client_test.go

@@ -257,16 +257,14 @@ func TestClientSyncBadID(t *testing.T) {
 	m := new(Msg)
 	m.SetQuestion("miek.nl.", TypeSOA)
 
+	// Test with client.Exchange, the plain Exchange function is just a wrapper, so
+	// we don't need to test that separately.
 	c := &Client{
-		Timeout: 50 * time.Millisecond,
+		Timeout: 10 * time.Millisecond,
 	}
 	if _, _, err := c.Exchange(m, addrstr); err == nil || !isNetworkTimeout(err) {
 		t.Errorf("query did not time out")
 	}
-	// And now with plain Exchange().
-	if _, err = Exchange(m, addrstr); err == nil || !isNetworkTimeout(err) {
-		t.Errorf("query did not time out")
-	}
 }
 
 func TestClientSyncBadThenGoodID(t *testing.T) {
@@ -290,14 +288,6 @@ func TestClientSyncBadThenGoodID(t *testing.T) {
 	if r.Id != m.Id {
 		t.Errorf("failed to get response with expected Id")
 	}
-	// And now with plain Exchange().
-	r, err = Exchange(m, addrstr)
-	if err != nil {
-		t.Errorf("failed to exchange: %v", err)
-	}
-	if r.Id != m.Id {
-		t.Errorf("failed to get response with expected Id")
-	}
 }
 
 func TestClientSyncTCPBadID(t *testing.T) {