Evas render: Fix another map clip render issue

Evas render: Fix another map clip render issue

This time it's only about performance. We seem to be setting the
changed flag too often, which might trigger unnecessary redraws.

- map flag is set if there is currently a map AND it's not an image
  object (because images can map themselves)
- hmap flag is set if there was a map before

So, map != hmap does not imply a transition between a mapped and
non-mapped state. Add an extra check before marking the clip
as dirty and changed.