reload: don't fail test on addr in use (#1804)

A bit meh, but we *need* hardcoded addresses in these tests, because
we can't get them from a running coredns. These may be in-use and this
fails the tests then. Do an ugly err.Error() string match if this is the
case to prevent failing the test for something not in our control.

A better fix would be to retreive the listening address from coredns via
some api, so we could listen on :0 for these as well. No such API exists
as of yet.

test/reload_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"io/ioutil"
 	"net/http"
+	"strings"
 	"testing"
 	"time"
 
@@ -65,10 +66,12 @@ func TestReloadHealth(t *testing.T) {
 }`
 	c, err := CoreDNSServer(corefile)
 	if err != nil {
+		if strings.Contains(err.Error(), inUse) {
+			return // meh, but don't error
+		}
 		t.Fatalf("Could not get service instance: %s", err)
 	}
 
-	// This fails with address 8080 already in use, it shouldn't.
 	if c1, err := c.Restart(NewInput(corefile)); err != nil {
 		t.Fatal(err)
 	} else {
@@ -85,6 +88,9 @@ func TestReloadMetricsHealth(t *testing.T) {
 }`
 	c, err := CoreDNSServer(corefile)
 	if err != nil {
+		if strings.Contains(err.Error(), inUse) {
+			return // meh, but don't error
+		}
 		t.Fatalf("Could not get service instance: %s", err)
 	}
 
@@ -118,3 +124,5 @@ func TestReloadMetricsHealth(t *testing.T) {
 		t.Errorf("Failed to see %s in metric output", proc)
 	}
 }
+
+const inUse = "address already in use"