[VOL-2193] Create mocks for Kafka Client and Etcd

This commit consists of:
1) A kafka client mock that implements the kafka client interface
under voltha-lib-go/pkg/kafka/client.go
2) An embedded Etcd server that runs in-process and represents an
Etcd server.

Change-Id: I52a36132568e08c596bb4136918bebcb654a3b99
diff --git a/vendor/go.etcd.io/etcd/auth/options.go b/vendor/go.etcd.io/etcd/auth/options.go
new file mode 100644
index 0000000..f40b92d
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/auth/options.go
@@ -0,0 +1,192 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package auth
+
+import (
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"fmt"
+	"io/ioutil"
+	"time"
+
+	jwt "github.com/dgrijalva/jwt-go"
+)
+
+const (
+	optSignMethod = "sign-method"
+	optPublicKey  = "pub-key"
+	optPrivateKey = "priv-key"
+	optTTL        = "ttl"
+)
+
+var knownOptions = map[string]bool{
+	optSignMethod: true,
+	optPublicKey:  true,
+	optPrivateKey: true,
+	optTTL:        true,
+}
+
+var (
+	// DefaultTTL will be used when a 'ttl' is not specified
+	DefaultTTL = 5 * time.Minute
+)
+
+type jwtOptions struct {
+	SignMethod jwt.SigningMethod
+	PublicKey  []byte
+	PrivateKey []byte
+	TTL        time.Duration
+}
+
+// ParseWithDefaults will load options from the specified map or set defaults where appropriate
+func (opts *jwtOptions) ParseWithDefaults(optMap map[string]string) error {
+	if opts.TTL == 0 && optMap[optTTL] == "" {
+		opts.TTL = DefaultTTL
+	}
+
+	return opts.Parse(optMap)
+}
+
+// Parse will load options from the specified map
+func (opts *jwtOptions) Parse(optMap map[string]string) error {
+	var err error
+	if ttl := optMap[optTTL]; ttl != "" {
+		opts.TTL, err = time.ParseDuration(ttl)
+		if err != nil {
+			return err
+		}
+	}
+
+	if file := optMap[optPublicKey]; file != "" {
+		opts.PublicKey, err = ioutil.ReadFile(file)
+		if err != nil {
+			return err
+		}
+	}
+
+	if file := optMap[optPrivateKey]; file != "" {
+		opts.PrivateKey, err = ioutil.ReadFile(file)
+		if err != nil {
+			return err
+		}
+	}
+
+	// signing method is a required field
+	method := optMap[optSignMethod]
+	opts.SignMethod = jwt.GetSigningMethod(method)
+	if opts.SignMethod == nil {
+		return ErrInvalidAuthMethod
+	}
+
+	return nil
+}
+
+// Key will parse and return the appropriately typed key for the selected signature method
+func (opts *jwtOptions) Key() (interface{}, error) {
+	switch opts.SignMethod.(type) {
+	case *jwt.SigningMethodRSA, *jwt.SigningMethodRSAPSS:
+		return opts.rsaKey()
+	case *jwt.SigningMethodECDSA:
+		return opts.ecKey()
+	case *jwt.SigningMethodHMAC:
+		return opts.hmacKey()
+	default:
+		return nil, fmt.Errorf("unsupported signing method: %T", opts.SignMethod)
+	}
+}
+
+func (opts *jwtOptions) hmacKey() (interface{}, error) {
+	if len(opts.PrivateKey) == 0 {
+		return nil, ErrMissingKey
+	}
+	return opts.PrivateKey, nil
+}
+
+func (opts *jwtOptions) rsaKey() (interface{}, error) {
+	var (
+		priv *rsa.PrivateKey
+		pub  *rsa.PublicKey
+		err  error
+	)
+
+	if len(opts.PrivateKey) > 0 {
+		priv, err = jwt.ParseRSAPrivateKeyFromPEM(opts.PrivateKey)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if len(opts.PublicKey) > 0 {
+		pub, err = jwt.ParseRSAPublicKeyFromPEM(opts.PublicKey)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if priv == nil {
+		if pub == nil {
+			// Neither key given
+			return nil, ErrMissingKey
+		}
+		// Public key only, can verify tokens
+		return pub, nil
+	}
+
+	// both keys provided, make sure they match
+	if pub != nil && pub.E != priv.E && pub.N.Cmp(priv.N) != 0 {
+		return nil, ErrKeyMismatch
+	}
+
+	return priv, nil
+}
+
+func (opts *jwtOptions) ecKey() (interface{}, error) {
+	var (
+		priv *ecdsa.PrivateKey
+		pub  *ecdsa.PublicKey
+		err  error
+	)
+
+	if len(opts.PrivateKey) > 0 {
+		priv, err = jwt.ParseECPrivateKeyFromPEM(opts.PrivateKey)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if len(opts.PublicKey) > 0 {
+		pub, err = jwt.ParseECPublicKeyFromPEM(opts.PublicKey)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if priv == nil {
+		if pub == nil {
+			// Neither key given
+			return nil, ErrMissingKey
+		}
+		// Public key only, can verify tokens
+		return pub, nil
+	}
+
+	// both keys provided, make sure they match
+	if pub != nil && pub.Curve != priv.Curve &&
+		pub.X.Cmp(priv.X) != 0 && pub.Y.Cmp(priv.Y) != 0 {
+		return nil, ErrKeyMismatch
+	}
+
+	return priv, nil
+}