[test] make unittest_webconfig independant of CWD
if apphome is unset in ApptestConfiguration constructor, this later looks
for a 'data' directory in CWD, making this test runnable only from
web/test (and pytest do chdir before executing tests, so we did not noticed
this problem).
from os.path import join
assert __file__.endswith(join('scripts', 'script2.py')), __file__
assert '__main__' == __name__, __name__
assert ['-v'] == __args__, __args__