integ-cli: fix clock skew against remote test daemon

This fixes the `docker events`-related tests as they have been
failing due to clock skew between CI machine and test daemon on
some other machine (even 1-2 seconds of diff causes races as
we pass local time to --since/--until).

If we're running in same host, we keep using time.Now(), otherwise
we read the system time of the daemon from `/info` endpoint.

Fixes pretty much all events-related tests on windows CI.

Signed-off-by: Ahmet Alp Balkan <ahmetalpbalkan@gmail.com>

integration-cli/docker_utils.go

@@ -981,6 +981,32 @@ func readContainerFileWithExec(containerId, filename string) ([]byte, error) {
 	return []byte(out), err
 }
 
+// daemonTime provides the current time on the daemon host
+func daemonTime(t *testing.T) time.Time {
+	if isLocalDaemon {
+		return time.Now()
+	}
+
+	body, err := sockRequest("GET", "/info", nil)
+	if err != nil {
+		t.Fatal("daemonTime: failed to get /info: %v", err)
+	}
+
+	type infoJSON struct {
+		SystemTime string
+	}
+	var info infoJSON
+	if err = json.Unmarshal(body, &info); err != nil {
+		t.Fatalf("unable to unmarshal /info response: %v", err)
+	}
+
+	dt, err := time.Parse(time.RFC3339Nano, info.SystemTime)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return dt
+}
+
 func setupRegistry(t *testing.T) func() {
 	testRequires(t, RegistryHosting)
 	reg, err := newTestRegistryV2(t)