Fix the "integration" target in components/rendering.

This PR fixes https://trac.openmicroscopy.org.uk/ome/ticket/11514.

A more general discussion would be useful. I've tried removing the confusing ``integration.testng.xml`` files from components that do not have any tests in the "integration" group. That breaks the top-level "integration" target, but can be fixed by adding a no-op for each of the components under their "integration" target.
@joshmoore: Is that something we could do? That would then indicate that only unit tests are present in specific components.

/cc @mtbc