Instead of defining the CliRunner value in each test, we use a fixture.
The CliRunner is also configured with stdout and stderr separated
because mixing them will pose problem if we use stderr for other
purposes in tests, e.g. to emit log messages from a forth-coming HTTP
server.
* Change all replica status from `running` to `streaming`
* Add an option to pytest to change the state back to `running`
* Also tests the output of the script
* Add a quick test script for live clusters
The checks `cluster_config_has_changed` and `node_tl_has_changed` use a
state file to store the previous value of the config hash and the
timeline.
Previously the check would fail if something changed, but the new value
would be saved directly. This behavious has changed. The new value
is saved only if `--save` is passed to the check.
The mimics the way [check_pgactivity] manages this kind of checks.
[check_pgactivity]: https://github.com/OPMDG/check_pgactivity
