fix typo

Signed-off-by: allencloud <allen.sun@daocloud.io>

libnetwork/internal/kvstore/kvstore_manage.go

@@ -25,7 +25,7 @@ var (
 	}()
 )
 
-// NewStore creates a an instance of store
+// NewStore creates an instance of store
 func NewStore(backend store.Backend, addrs []string, options *store.Config) (store.Store, error) {
 	if init, exists := initializers[backend]; exists {
 		return init(addrs, options)