[bug 14185] Check that Homogeneity exceptions are still present.

Related to bug 14185.

This merge request enhance the rake valid:homogeneity task.

This task will check that differences between nodes that have been registered into the lib/refrepo/valid/data/homogeneity.yaml.erb file are present into the ref-repo. If an exception from the previous file is not found in the ref-repo, it is counted as an error.

The goal of this merge request is to avoid the exceptions in the homogeneity.yaml.erb file to stale and lead us to confusion.

This merge requests contains:

• Fixes to the exceptions that are outdated (nodes properties are marked as differents, while they are homogeneous in ref-repo)
• Enhancement of the rake valid:homogeneity tasks
• Adding of the rake valid:homogeneity task to the validate pipeline of the CI, to check regularly that no errors are introduced in the repo.