rgw/notification: For kafka include user-id & password as part of the key along with...

rgw/notification: For kafka include user-id & password as part of the key along with endpoint for connection pooling.

For kafka, currently connection pooling is done based on endpoint, so all the events with same endpoint share the same connection. but there are issues when userid & password is created/changed for the endpoint, coz the old connection is cached in broker manager and when new event with updated/new userid-password is sent, broker still uses the old connection that was created with old/no userid/password as currently only the `endpoint` is the key to connection pool.
To fix this, use all the topic attributes that are part of connection as the key to connection pool and if any of the attribute changes create new kafka connection. Attibutes include userid, password, ssl, ca_laction.

Signed-off-by: kchheda3 <kchheda3@bloomberg.net>