[20.10] integration/daemon: fix missing import

commit 44152f6fb6 backported a change
that added `os.TempDir()` to a test, but that import was not yet
in this file in the 20.10 branch.

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

integration/daemon/daemon_test.go

@@ -2,6 +2,7 @@ package daemon // import "github.com/docker/docker/integration/daemon"
 
 import (
 	"context"
+	"os"
 	"runtime"
 	"testing"