check for SCALA_CONTAINER in Java-flavored projects

This is an update to the test to add `autoScalaLibrary := false` to the test Java project, and make sure that the generated `.classpath` file lacks a `SCALA_CONTAINER` entry.

It would be nice if there were a simple way for setting `EclipseKeys.projectFlavor := EclipseProjectFlavor.Java` to automatically add the setting `autoScalaLibrary := false` to the project, but I can't find a clean way to do it.