charm fails to query mysql, mysql running leader-settings-changed

One of three gnocchi units went into an error state because it lost connection to mysql during a query. At the same time, the mysql-innodb-cluster is reporting that it is performing a server shutdown during the leader-settings-changed hook.

Im not sure if either gnocchi or mysql-innodb-router should defer/retry the request till the hook has finished, or if mysql-innodb-cluster should defer the hook until the requests have been made.

Gnocchi_0 upgrade log shows:
2021-05-19 13:31:59,256 [113103] CRITICAL root: Traceback (most recent call last):
....
  File "/usr/lib/python3/dist-packages/pymysql/connections.py", line 657, in _read_packet
    packet_header = self._read_bytes(4)
  File "/usr/lib/python3/dist-packages/pymysql/connections.py", line 706, in _read_bytes
    raise err.OperationalError(
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2013, 'Lost connection to MySQL server during query')
[SQL: SHOW VARIABLES LIKE 'sql_mode']
(Background on this error at: http://sqlalche.me/e/e3q8)

and at the same time mysql-innodb-cluster_0 shows:
2021-05-19 13:31:58 DEBUG jujuc server.go:211 running hook tool "network-get" for mysql-innodb-cluster/0-leader-settings-changed-7576194136442783270
2021-05-19 13:31:59 DEBUG jujuc server.go:211 running hook tool "juju-log" for mysql-innodb-cluster/0-leader-settings-changed-7576194136442783270
2021-05-19 13:31:59 ERROR juju-log Failed checking cluster status: Cannot set LC_ALL to locale en_US.UTF-8: No such file or directory
Traceback (most recent call last):
  File "<string>", line 3, in <module>
mysqlsh.DBError: MySQL Error (1053): Cluster.status: Failed to execute query on Metadata server 192.168.33.211:3306: Server shutdown in progress

2021-05-19 13:31:59 DEBUG jujuc server.go:211 running hook tool "status-set" for mysql-innodb-cluster/0-leader-settings-changed-7576194136442783270
2021-05-19 13:31:59 DEBUG jujuc server.go:211 running hook tool "is-leader" for mysql-innodb-cluster/0-leader-settings-changed-7576194136442783270
2021-05-19 13:31:59 DEBUG jujuc server.go:211 running hook tool "is-leader" for mysql-innodb-cluster/0-leader-settings-changed-7576194136442783270

Crashdump at https://oil-jenkins.canonical.com/artifacts/fddd8b11-9429-41e2-a98b-90b94abe1785/generated/generated/openstack/juju-crashdump-openstack-2021-05-19-13.36.28.tar.gz

and full test run at:
https://solutions.qa.canonical.com/testruns/testRun/fddd8b11-9429-41e2-a98b-90b94abe1785