Fix test execution when running in standalone mode.

Fix errors:

* AttributeError: 'NoneType' object has no attribute 'unique_id'
* AttributeError: 'NoneType' object has no attribute 'keep_tmp_files'

When running tests standalone, like:

python tests/sleeptest/sleeptest.py

Signed-off-by: Ruda Moura <rmoura@redhat.com>