Allow empty Redis config
Allow empty Redis config

When Redis config is empty, use defaults.
However when a Redis cluster config is specified, the "seeds" attribute
is mandatory.

Signed-off-by: Vincent Petry <87e1f221a672a14a323e57bb65eaea19d3ed3804@nextcloud.com>

nextcloud/server,nextcloud/server,nextcloud/server,nextcloud/server