integration: Add a new networking integration test suite

This commit introduces a new integration test suite aimed at testing
networking features like inter-container communication, network
isolation, port mapping, etc... and how they interact with daemon-level
and network-level parameters.

So far, there's pretty much no tests making sure our networks are well
configured: 1. there're a few tests for port mapping, but they don't
cover all use cases ; 2. there're a few tests that check if a specific
iptables rule exist, but that doesn't prevent that specific iptables
rule to be wrong in the first place.

As we're planning to refactor how iptables rules are written, and change
some of them to fix known security issues, we need a way to test all
combinations of parameters. So far, this was done by hand, which is
particularly painful and time consuming. As such, this new test suite is
foundational to upcoming work.

Signed-off-by: Albin Kerouanton <albinker@gmail.com>
(cherry picked from commit 409ea70)
Signed-off-by: Cory Snider <csnider@mirantis.com>

integration/networking/main_test.go

@@ -0,0 +1,34 @@
+package networking
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/docker/docker/testutil/environment"
+)
+
+var testEnv *environment.Execution
+
+func TestMain(m *testing.M) {
+	var err error
+	testEnv, err = environment.New()
+	if err != nil {
+		panic(err)
+	}
+
+	err = environment.EnsureFrozenImagesLinux(testEnv)
+	if err != nil {
+		panic(err)
+	}
+
+	testEnv.Print()
+	code := m.Run()
+	os.Exit(code)
+}
+
+func setupTest(t *testing.T) context.Context {
+	environment.ProtectAll(t, testEnv)
+	t.Cleanup(func() { testEnv.Clean(t) })
+	return context.Background()
+}