fix examples/ compilation so that test/ also compiles

fix network-tester cauldron serve_hostnames

examples/explorer/BUILD

@@ -0,0 +1,15 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_binary",
+)
+
+go_binary(
+    name = "explorer",
+    srcs = ["explorer.go"],
+    tags = ["automanaged"],
+    deps = ["//vendor:github.com/davecgh/go-spew/spew"],
+)