[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/github.com/json-iterator/go/any_uint32.go b/vendor/github.com/json-iterator/go/any_uint32.go
new file mode 100644
index 0000000..656bbd3
--- /dev/null
+++ b/vendor/github.com/json-iterator/go/any_uint32.go
@@ -0,0 +1,74 @@
+package jsoniter
+
+import (
+	"strconv"
+)
+
+type uint32Any struct {
+	baseAny
+	val uint32
+}
+
+func (any *uint32Any) LastError() error {
+	return nil
+}
+
+func (any *uint32Any) ValueType() ValueType {
+	return NumberValue
+}
+
+func (any *uint32Any) MustBeValid() Any {
+	return any
+}
+
+func (any *uint32Any) ToBool() bool {
+	return any.val != 0
+}
+
+func (any *uint32Any) ToInt() int {
+	return int(any.val)
+}
+
+func (any *uint32Any) ToInt32() int32 {
+	return int32(any.val)
+}
+
+func (any *uint32Any) ToInt64() int64 {
+	return int64(any.val)
+}
+
+func (any *uint32Any) ToUint() uint {
+	return uint(any.val)
+}
+
+func (any *uint32Any) ToUint32() uint32 {
+	return any.val
+}
+
+func (any *uint32Any) ToUint64() uint64 {
+	return uint64(any.val)
+}
+
+func (any *uint32Any) ToFloat32() float32 {
+	return float32(any.val)
+}
+
+func (any *uint32Any) ToFloat64() float64 {
+	return float64(any.val)
+}
+
+func (any *uint32Any) ToString() string {
+	return strconv.FormatInt(int64(any.val), 10)
+}
+
+func (any *uint32Any) WriteTo(stream *Stream) {
+	stream.WriteUint32(any.val)
+}
+
+func (any *uint32Any) Parse() *Iterator {
+	return nil
+}
+
+func (any *uint32Any) GetInterface() interface{} {
+	return any.val
+}