remove testify dependency through mock package

Signed-off-by: Alexandre Beslic <abronan@docker.com>

libnetwork/internal/kvstore/kvstore.go

@@ -10,8 +10,6 @@ import (
 type Backend string
 
 const (
-	// MOCK backend
-	MOCK Backend = "mock"
 	// CONSUL backend
 	CONSUL = "consul"
 	// ETCD backend

libnetwork/internal/kvstore/kvstore_manage.go

@@ -4,7 +4,6 @@ import (
 	"github.com/docker/libkv/store"
 	"github.com/docker/libkv/store/consul"
 	"github.com/docker/libkv/store/etcd"
-	"github.com/docker/libkv/store/mock"
 	"github.com/docker/libkv/store/zookeeper"
 )
 
@@ -14,10 +13,9 @@ type Initialize func(addrs []string, options *store.Config) (store.Store, error)
 var (
 	// Backend initializers
 	initializers = map[store.Backend]Initialize{
-		store.MOCK:   mock.InitializeMock,
-		store.CONSUL: consul.InitializeConsul,
-		store.ETCD:   etcd.InitializeEtcd,
-		store.ZK:     zookeeper.InitializeZookeeper,
+		store.CONSUL: consul.New,
+		store.ETCD:   etcd.New,
+		store.ZK:     zookeeper.New,
 	}
 )