Make TestEventsFilterLabels less flaky

This test sometimes failed because the number of events received did not
match the expected number:

    FAIL: docker_cli_events_test.go:316: DockerSuite.TestEventsFilterLabels

    docker_cli_events_test.go:334:
        c.Assert(len(events), checker.Equals, 3)
    ... obtained int = 2
    ... expected int = 3

This patch makes the test more stable, by:

- use a wider range between `--since` and `--until`. These options were set
  so that the client detaches after events were received, but the actual
  range should not matter. Changing the range will cause more events to be
  returned, but we're specifically looking for the container ID's, so this
  should not make a difference for the actual test.
- use `docker create` instead of `docker run` for the containers. the
  containers don't have to be running to trigger an event; using `create`
  speeds up the test.
- check the exit code of the `docker create` to verify the containers were
  succesfully created.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

integration-cli/docker_cli_events_test.go

@@ -9,6 +9,7 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"strconv"
 	"strings"
 	"time"
 
@@ -314,29 +315,38 @@ func (s *DockerSuite) TestEventsFilterImageName(c *check.C) {
 }
 
 func (s *DockerSuite) TestEventsFilterLabels(c *check.C) {
-	since := daemonUnixTime(c)
+	since := strconv.FormatUint(uint64(daemonTime(c).Unix()), 10)
 	label := "io.docker.testing=foo"
 
-	out, _ := dockerCmd(c, "run", "-d", "-l", label, "busybox:latest", "true")
+	out, exit := dockerCmd(c, "create", "-l", label, "busybox")
+	c.Assert(exit, checker.Equals, 0)
 	container1 := strings.TrimSpace(out)
 
-	out, _ = dockerCmd(c, "run", "-d", "busybox", "true")
+	out, exit = dockerCmd(c, "create", "busybox")
+	c.Assert(exit, checker.Equals, 0)
 	container2 := strings.TrimSpace(out)
 
+	// fetch events with `--until`, so that the client detaches after a second
+	// instead of staying attached, waiting for more events to arrive.
 	out, _ = dockerCmd(
 		c,
 		"events",
 		"--since", since,
-		"--until", daemonUnixTime(c),
+		"--until", strconv.FormatUint(uint64(daemonTime(c).Add(time.Second).Unix()), 10),
-		"--filter", fmt.Sprintf("label=%s", label))
+		"--filter", "label="+label,
+	)
 
 	events := strings.Split(strings.TrimSpace(out), "\n")
-	c.Assert(len(events), checker.Equals, 3)
+	c.Assert(len(events), checker.GreaterThan, 0)
 
+	var found bool
 	for _, e := range events {
-		c.Assert(e, checker.Contains, container1)
+		if strings.Contains(e, container1) {
+			found = true
+		}
 		c.Assert(e, checker.Not(checker.Contains), container2)
 	}
+	c.Assert(found, checker.Equals, true)
 }
 
 func (s *DockerSuite) TestEventsFilterImageLabels(c *check.C) {