docker: codestyle pep8 subtest.py

Signed-off-by: Jiří Župka <jzupka@redhat.com>
dockertest: Make SubSubtestCaller more simple and adds simultaneous version.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
Docker: fix typo and code style in subtests

Signed-off-by: Jiří Župka <jzupka@redhat.com>
docker: Fix change SubSubtestCaller to old simultaneous version to keep compatibility.

Signed-off-by: Jiří Župka <jzupka@redhat.com>