Replace usage of old incubator configuration generator by the
oslo.config tool.
tools/config/generate_sample.sh has been replaced by tox -egenconfig.
heat_integrationtests/generate_sample.sh has been replaced by
oslo-config-generator
--config-file=heat_integrationtests/config-generator.conf
Change-Id: I6d95df203b556c8ec2088d40a446427f7087b9a7