qtest.py: Few pylint/style fixes

No actual code changes, just few pylint/style fixes.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20170818142613.32394-11-ldoktor@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>