Disable download logs in Maven by default
This commit adds a flag to Maven by default, which disables the messages
like "Downloading from central".
The logger is set to level "warn", so errors will still be visible, but
successful messages won't clutter logs anymore.
This option is also set by default in the GitLab CI template file for
maven.
See [1] for reference on the option.
1: https://stackoverflow.com/a/35653426/8843830
Starting point for that refactoring: it turned out that the tests
was not independent. The DefaultValueCache which is a singleton
keeps the status over various tests. Success of test execution depends
on the order test execution.
We have now
* a dedicated rule for resetting the default value cache
* JenkinsConfiguration rule (which already provided facilities for
dealing with the configuration) has been replaced by a readYaml rule.
From the PipelineUnit test framework we get already a handler for
libraryResource, which is also part of the setup of the default
values.
* An auxiliar class which combines the
* JenkinsSetupRule (registers the lib)
* JenkinsReadYamlRule (provides facilities for Yaml parsing)
* JenkinsResetDefaultValueCacheRule (cleans up the DefaultValueCache)
into a rule chain. By using this rule chain we ensure that our
setup OK (piper lib registered, and default config can be setup in
a clean way).
