Switched back to "jenkinsci" to be on safe side

The tests will fail now until the required branches are
available in jenkinsci! For local tests you can switch
"jenkinsci" to "alexanderlink".

You have to decide how to handle tests!
Currently the productive repo is cloned for testing...
Changed test branches from "test/..." to "tests/..."

+ small refactoring
Merge branch 'test/namespace3/master' of https://github.com/alexanderlink/git-client-plugin into proto-fix-namespace-change-detection

Conflicts:
	src/test/java/org/jenkinsci/plugins/gitclient/GitAPITestCase.java