Tempest test for 'rebuild'

[hongbin]

Recently, Zun introduces a 'rebuild' feature: https://review.openstack.org/#/c/551429/ . We need to add a tempest test for verifying this feature.

Note:
* You can find the Zun's tempest tests in https://github.com/openstack/zun-tempest-plugin/blob/master/zun_tempest_plugin/tests/tempest/api/test_containers.py
* This is the guide for how to run tempest test: https://docs.openstack.org/zun/latest/contributor/tempest-tests.html