Fix stdout premature EOF

Never close attached stream before both stdout and stderr have written
all their buffered contents. Remove stdinCloser because it is not needed
any more as the stream is closed anyway after attach has finished.

Fixes #3631

Signed-off-by: Andy Goldstein <agoldste@redhat.com>

integration-cli/docker_cli_run_test.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net"
 	"os"
@@ -2446,3 +2447,46 @@ func TestRunVolumesCleanPaths(t *testing.T) {
 
 	logDone("run - volume paths are cleaned")
 }
+
+// Regression test for #3631
+func TestRunSlowStdoutConsumer(t *testing.T) {
+	defer deleteAllContainers()
+
+	c := exec.Command("/bin/bash", "-c", dockerBinary+` run --rm -i busybox /bin/sh -c "dd if=/dev/zero of=/foo bs=1024 count=2000 &>/dev/null; catv /foo"`)
+
+	stdout, err := c.StdoutPipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := c.Start(); err != nil {
+		t.Fatal(err)
+	}
+	n, err := consumeSlow(stdout, 10000, 5*time.Millisecond)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := 2 * 1024 * 2000
+	if n != expected {
+		t.Fatalf("Expected %d, got %d", expected, n)
+	}
+
+	logDone("run - slow consumer")
+}
+
+func consumeSlow(reader io.Reader, chunkSize int, interval time.Duration) (n int, err error) {
+	buffer := make([]byte, chunkSize)
+	for {
+		var readBytes int
+		readBytes, err = reader.Read(buffer)
+		n += readBytes
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+			}
+			return
+		}
+		time.Sleep(interval)
+	}
+}