This was introduced by #2990: pod cannot be started and show the
following logs:
```
2023-12-26 03:29:25.569 UTC [47] CONTEXT: SQL statement "CREATE DATABASE "citus""
PL/pgSQL function inline_code_block line 5 at SQL statement
2023-12-26 03:29:25.569 UTC [47] STATEMENT: DO $$
BEGIN
PERFORM * FROM pg_catalog.pg_database WHERE datname = 'citus';
IF NOT FOUND THEN
CREATE DATABASE "citus";
END IF;
END;$$
2023-12-26 03:29:25,570 ERROR: post_bootstrap
Traceback (most recent call last):
File "/usr/local/lib/python3.11/dist-packages/patroni/postgresql/bootstrap.py", line 474, in post_bootstrap
self._postgresql.citus_handler.bootstrap()
File "/usr/local/lib/python3.11/dist-packages/patroni/postgresql/mpp/citus.py", line 401, in bootstrap
cur.execute(sql.encode('utf-8'))
psycopg2.errors.ActiveSqlTransaction: CREATE DATABASE cannot be executed from a function
CONTEXT: SQL statement "CREATE DATABASE "citus""
PL/pgSQL function inline_code_block line 5 at SQL statement
```
---------
Signed-off-by: Zhao Junwang <[email protected]>
PR #2909 remove the cache in Zookeeper implementation of DCS, so
the comment of get_cluster should be changed to 'Retrieve a fresh
view of DCS' since every implementation does so.
Signed-off-by: Zhao Junwang <[email protected]>
