[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/spf13/pflag/uint.go b/vendor/github.com/spf13/pflag/uint.go
new file mode 100644
index 0000000..dcbc2b7
--- /dev/null
+++ b/vendor/github.com/spf13/pflag/uint.go
@@ -0,0 +1,88 @@
+package pflag
+
+import "strconv"
+
+// -- uint Value
+type uintValue uint
+
+func newUintValue(val uint, p *uint) *uintValue {
+	*p = val
+	return (*uintValue)(p)
+}
+
+func (i *uintValue) Set(s string) error {
+	v, err := strconv.ParseUint(s, 0, 64)
+	*i = uintValue(v)
+	return err
+}
+
+func (i *uintValue) Type() string {
+	return "uint"
+}
+
+func (i *uintValue) String() string { return strconv.FormatUint(uint64(*i), 10) }
+
+func uintConv(sval string) (interface{}, error) {
+	v, err := strconv.ParseUint(sval, 0, 0)
+	if err != nil {
+		return 0, err
+	}
+	return uint(v), nil
+}
+
+// GetUint return the uint value of a flag with the given name
+func (f *FlagSet) GetUint(name string) (uint, error) {
+	val, err := f.getFlagType(name, "uint", uintConv)
+	if err != nil {
+		return 0, err
+	}
+	return val.(uint), nil
+}
+
+// UintVar defines a uint flag with specified name, default value, and usage string.
+// The argument p points to a uint variable in which to store the value of the flag.
+func (f *FlagSet) UintVar(p *uint, name string, value uint, usage string) {
+	f.VarP(newUintValue(value, p), name, "", usage)
+}
+
+// UintVarP is like UintVar, but accepts a shorthand letter that can be used after a single dash.
+func (f *FlagSet) UintVarP(p *uint, name, shorthand string, value uint, usage string) {
+	f.VarP(newUintValue(value, p), name, shorthand, usage)
+}
+
+// UintVar defines a uint flag with specified name, default value, and usage string.
+// The argument p points to a uint  variable in which to store the value of the flag.
+func UintVar(p *uint, name string, value uint, usage string) {
+	CommandLine.VarP(newUintValue(value, p), name, "", usage)
+}
+
+// UintVarP is like UintVar, but accepts a shorthand letter that can be used after a single dash.
+func UintVarP(p *uint, name, shorthand string, value uint, usage string) {
+	CommandLine.VarP(newUintValue(value, p), name, shorthand, usage)
+}
+
+// Uint defines a uint flag with specified name, default value, and usage string.
+// The return value is the address of a uint  variable that stores the value of the flag.
+func (f *FlagSet) Uint(name string, value uint, usage string) *uint {
+	p := new(uint)
+	f.UintVarP(p, name, "", value, usage)
+	return p
+}
+
+// UintP is like Uint, but accepts a shorthand letter that can be used after a single dash.
+func (f *FlagSet) UintP(name, shorthand string, value uint, usage string) *uint {
+	p := new(uint)
+	f.UintVarP(p, name, shorthand, value, usage)
+	return p
+}
+
+// Uint defines a uint flag with specified name, default value, and usage string.
+// The return value is the address of a uint  variable that stores the value of the flag.
+func Uint(name string, value uint, usage string) *uint {
+	return CommandLine.UintP(name, "", value, usage)
+}
+
+// UintP is like Uint, but accepts a shorthand letter that can be used after a single dash.
+func UintP(name, shorthand string, value uint, usage string) *uint {
+	return CommandLine.UintP(name, shorthand, value, usage)
+}