Dns.join (#944)

* Add dnsutil.Join

* Create dnsutil.Join

Create Join helper function and move bits in the code over.

middleware/etcd/stub.go

@@ -4,10 +4,10 @@ import (
 	"log"
 	"net"
 	"strconv"
-	"strings"
 	"time"
 
 	"github.com/coredns/coredns/middleware/etcd/msg"
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
 	"github.com/coredns/coredns/middleware/proxy"
 	"github.com/coredns/coredns/request"
 
@@ -62,7 +62,7 @@ Services:
 			// Chop of left most label, because that is used as the nameserver place holder
 			// and drop the right most labels that belong to zone.
 			// We must *also* chop of dns.stub. which means cutting two more labels.
-			domain = dns.Fqdn(strings.Join(labels[1:len(labels)-dns.CountLabel(z)-2], "."))
+			domain = dnsutil.Join(labels[1 : len(labels)-dns.CountLabel(z)-2])
 			if domain == z {
 				log.Printf("[WARNING] Skipping nameserver for domain we are authoritative for: %s", domain)
 				continue Services