Dns.join (#944)

* Add dnsutil.Join

* Create dnsutil.Join

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

middleware/etcd/msg/path.go

@@ -4,6 +4,8 @@ import (
 	"path"
 	"strings"
 
+	"github.com/coredns/coredns/middleware/pkg/dnsutil"
+
 	"github.com/miekg/dns"
 )
 
@@ -24,7 +26,7 @@ func Domain(s string) string {
 	for i, j := 1, len(l)-1; i < j; i, j = i+1, j-1 {
 		l[i], l[j] = l[j], l[i]
 	}
-	return dns.Fqdn(strings.Join(l[1:len(l)-1], "."))
+	return dnsutil.Join(l[1 : len(l)-1])
 }
 
 // PathWithWildcard ascts as Path, but if a name contains wildcards (* or any), the name will be