Port multiple attach test to cli tests

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

integration-cli/docker_cli_attach_test.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"os/exec"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestMultipleAttachRestart(t *testing.T) {
+	cmd := exec.Command(dockerBinary, "run", "--name", "attacher", "-d", "busybox",
+		"/bin/sh", "-c", "sleep 1 && echo hello")
+
+	group := sync.WaitGroup{}
+	group.Add(4)
+
+	go func() {
+		defer group.Done()
+		out, _, err := runCommandWithOutput(cmd)
+		if err != nil {
+			t.Fatal(err, out)
+		}
+	}()
+	time.Sleep(500 * time.Millisecond)
+
+	for i := 0; i < 3; i++ {
+		go func() {
+			defer group.Done()
+			c := exec.Command(dockerBinary, "attach", "attacher")
+
+			out, _, err := runCommandWithOutput(c)
+			if err != nil {
+				t.Fatal(err, out)
+			}
+			if actual := strings.Trim(out, "\r\n"); actual != "hello" {
+				t.Fatalf("unexpected output %s expected hello", actual)
+			}
+		}()
+	}
+
+	group.Wait()
+
+	cmd = exec.Command(dockerBinary, "kill", "attacher")
+	if _, err := runCommand(cmd); err != nil {
+		t.Fatal(err)
+	}
+	deleteAllContainers()
+
+	logDone("run - multiple attach")
+}