Cope with '%' in password when waiting for migrations (#12440)

(cherry picked from commit d4c3d32)

Author: highfly22

chart/templates/_helpers.yaml

@@ -380,7 +380,7 @@ server_tls_key_file = /etc/pgbouncer/server.key
         directory = os.path.join(package_dir, 'migrations')
         config = Config(os.path.join(package_dir, 'alembic.ini'))
         config.set_main_option('script_location', directory)
-        config.set_main_option('sqlalchemy.url', settings.SQL_ALCHEMY_CONN)
+        config.set_main_option('sqlalchemy.url', settings.SQL_ALCHEMY_CONN.replace('%', '%%'))
         script_ = ScriptDirectory.from_config(config)
 
         timeout=60