Standby leaders in v3.0.4 or above are not recognized

[mbanck]

The fix for #28 (PR #30) did not take Standby leaders into accunt; the code in the ClusterHasLeader class is as follows:

        is_leader_found = False
        for member in item_dict["members"]:
            if (
                member["role"] in ("leader", "standby_leader")
                and member["state"] == "running"
            ):
                is_leader_found = True
                break

However, Standby leaders (since Patroni v3.0.4) now also have state streaming not running, resulting in a failed check for cluster_has_leader:

$ sudo patronictl -c /etc/patroni/13-production.yml list
+ Cluster: 13-production ----------------+-----------+----+-----------+
| Member  | Host        | Role           | State     | TL | Lag in MB |
+---------+-------------+----------------+-----------+----+-----------+
| db-pg01 | 10.111.11.1 | Replica        | streaming |  8 |         0 |
| db-pg02 | 10.111.11.2 | Standby Leader | streaming |  8 |           |
+---------+-------------+----------------+-----------+----+-----------+
$ sudo check_patroni -e https://127.0.0.1:8008 cluster_has_leader
CLUSTERHASLEADER CRITICAL - The cluster has no running leader. | has_leader=0;;@0