Before this patch we checked the expected standby leader state
was `running` for all versions of Patroni.
With this patch, for:
* Patroni < 3.0.4, standby leaders are in `running` state.
* Patroni >= 3.0.4, standby leaders can be in `streaming` or `in
archive recovey` state. We will raise a warning for the latter.
The tests where modified to account for this.
Co-authored-by: Denis Laxalde <denis@laxalde.org>
