tests: functional as a package

I added __init__.py to functional tests' folder, so now we can
import its modules from unit tests.

Change-Id: Ie3dd85be81b471a9699e0ef3633ad2d13ca442c9
Signed-off-by: Petr Horáček <phoracek@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/31165
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>