Fix image preloading

tests/preload_test.go

@@ -0,0 +1,23 @@
+package integration
+
+import (
+	. "gopkg.in/check.v1"
+)
+
+func (s *QemuSuite) TestPreload(c *C) {
+	err := s.RunQemu()
+	c.Assert(err, IsNil)
+
+	s.CheckCall(c, `
+docker pull busybox
+sudo docker save -o /var/lib/rancher/preload/system-docker/busybox.tar busybox
+sudo system-docker pull alpine
+sudo system-docker save -o /var/lib/rancher/preload/docker/alpine.tar alpine`)
+
+	s.Reboot(c)
+
+	s.CheckCall(c, `
+sleep 5
+sudo system-docker images | grep busybox
+docker images | grep alpine`)
+}