Add exit return code for unit tests

Add exit return code for unit tests

Note that this patch should trigger some refactoring
1: repo structure, uggly hack due to the fact that the code
is at the root of the repo. The name can be change when cloning
leading to python path issues

2: logger is called with harcoded file in functest_logger.py
uggly hack to create the file is not already present

Basically hacks were necessary to be able to run the unit tests
locally and from jenkins

JIRA: FUNCTEST-336

Change-Id: Ib88256a167c003805d480f57c218c37d8d5962d8
Signed-off-by: Morgan Richomme <morgan.richomme@orange.com>