Swift/ideas/more-testing-devices

Probe tests with more devices

For LP Bug: 1675500 and to detect later bugs is necessary to use more than 4 devices in probe tests. It can be useful to update the default development environment and existing probtests to use 8 devices and then finish probe tests draft of container/account DB replication https://review.openstack.org/#/c/448480/11/test/probe/test_db_replication.py