Add VM infrastructure smoke test

This adds an E2E test which exercises the VM infrastructure (Kubernetes, KVM device plugin and QEMU).
This test should ensure that nobody breaks the core infrastructure Metropolis VMs rely on.

Test Plan: This is a test

X-Origin-Diff: phab/D740
GitOrigin-RevId: ddf629725dfb664ace5a50efee9ed9442962d6f7
diff --git a/metropolis/vm/smoketest/payload/main.go b/metropolis/vm/smoketest/payload/main.go
new file mode 100644
index 0000000..2ea6485
--- /dev/null
+++ b/metropolis/vm/smoketest/payload/main.go
@@ -0,0 +1,36 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func main() {
+	if err := unix.Mount("devtmpfs", "/dev", "devtmpfs", 0, ""); err != nil {
+		panic(err)
+	}
+	testPort, err := os.OpenFile("/dev/vport1p1", os.O_RDWR, 0)
+	if err != nil {
+		panic(err)
+	}
+	testPort.WriteString("test123")
+	testPort.Close()
+	unix.Reboot(unix.LINUX_REBOOT_CMD_POWER_OFF)
+}