MultiModuleUpdatePomsTest should verify generate features ran

[turkeylurkey]

After initiating a rebuild due to the build file being updated generate features should run but it should generate the same features. This can be detected in the console log as a message similar to "Regenerate the following features: [a, b, c]".

Currently we just verify that the file is not changed:

      // verify that feature generation regenerates the same features
      assertEquals("generated-features.xml was modified\n" + getLogTail(), newFeatureFileLastModified, newFeatureFile.lastModified());

Verify instead that the message is generated.