[FIX] Do not rollback failing tests for the moment:

XML and YAML files are all loaded in the same transaction.
We should add a section for tests in __terp__ and load each test file
in its own transaction so that:
- they are independent from each other,
- failing tests can safely be rolled back,
- all tests can still be run in one pass.

bzr revid: jth@openerp.com-20100309172147-m0rkmc30yjae2605