Fix GerritProjectListTest to have no dependency on the tests execution order

Sometimes, the testAddProject is not first one executed and this is why the 2 other
test cases are failing. Implemented before and after methods to setup and teardown
anything required by the test cases so they no longer depends on testAddProject to
be executed first.
Merge pull request #78 from hugares/fix-failing-tests

Fix GerritProjectListTest to have no dependency on the tests execution order