Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/json-iterator/go/Gopkg.lock

@@ -0,0 +1,27 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/json-iterator/go"
+  packages = ["."]
+  revision = "ca39e5af3ece67bbcda3d0f4f56a8e24d9f2dad4"
+  version = "1.1.3"
+
+[[projects]]
+  name = "github.com/modern-go/concurrent"
+  packages = ["."]
+  revision = "e0a39a4cb4216ea8db28e22a69f4ec25610d513a"
+  version = "1.0.0"
+
+[[projects]]
+  name = "github.com/modern-go/reflect2"
+  packages = ["."]
+  revision = "1df9eeb2bb81f327b96228865c5687bc2194af3f"
+  version = "1.0.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "56a0b9e9e61d2bc8af5e1b68537401b7f4d60805eda3d107058f3171aa5cf793"
+  solver-name = "gps-cdcl"
+  solver-version = 1