Use common TLS parsing routine for etcd (#476)

* Use common TLS parsing routine for etcd

Change to use the new common routine, and update the docs to reflect
the different options for passing TLS configuration.

* Move middleware/tls to middleware/pkg/tls

This was put in the wrong place originally.

middleware/pkg/tls/tls_test.go

@@ -0,0 +1,81 @@
+package tls
+
+import (
+        "testing"
+        "path/filepath"
+
+	"github.com/miekg/coredns/middleware/test"
+)
+
+func getPEMFiles(t *testing.T) (rmFunc func(), cert, key, ca string) {
+	tempDir, rmFunc, err := test.WritePEMFiles("")
+	if err != nil {
+		t.Fatalf("Could not write PEM files: %s", err)
+	}
+
+	cert = filepath.Join(tempDir, "cert.pem")
+	key = filepath.Join(tempDir, "key.pem")
+	ca = filepath.Join(tempDir, "ca.pem")
+
+	return
+}
+
+func TestNewTLSConfig(t *testing.T) {
+	rmFunc, cert, key, ca := getPEMFiles(t)
+	defer rmFunc()
+
+	_, err := NewTLSConfig(cert, key, ca)
+	if err != nil {
+		t.Errorf("Failed to create TLSConfig: %s", err)
+	}
+}
+
+func TestNewTLSClientConfig(t *testing.T) {
+	rmFunc, _, _, ca := getPEMFiles(t)
+	defer rmFunc()
+
+	_, err := NewTLSClientConfig(ca)
+	if err != nil {
+		t.Errorf("Failed to create TLSConfig: %s", err)
+	}
+}
+
+func TestNewTLSConfigFromArgs(t *testing.T) {
+	rmFunc, cert, key, ca := getPEMFiles(t)
+	defer rmFunc()
+
+	_, err := NewTLSConfigFromArgs()
+	if err != nil {
+		t.Errorf("Failed to create TLSConfig: %s", err)
+	}
+
+	c, err := NewTLSConfigFromArgs(ca)
+	if err != nil {
+		t.Errorf("Failed to create TLSConfig: %s", err)
+	}
+	if c.RootCAs == nil {
+		t.Error("RootCAs should not be nil when one arg passed")
+	}
+
+	c, err = NewTLSConfigFromArgs(cert,key)
+	if err != nil {
+		t.Errorf("Failed to create TLSConfig: %s", err)
+	}
+	if c.RootCAs != nil {
+		t.Error("RootCAs should be nil when two args passed")
+	}
+	if len(c.Certificates) != 1 {
+		t.Error("Certificates should have a single entry when two args passed")
+	}
+	args := []string{cert,key,ca}
+	c, err = NewTLSConfigFromArgs(args...)
+	if err != nil {
+		t.Errorf("Failed to create TLSConfig: %s", err)
+	}
+	if c.RootCAs == nil {
+		t.Error("RootCAs should not be nil when three args passed")
+	}
+	if len(c.Certificates) != 1 {
+		t.Error("Certificateis should have a single entry when three args passed")
+	}
+}