loadbalancer: fail on failed "Wait for backup * to start" handlers
If a faulty HAProxy/ProxySQL configuration is applied and the backup HAProxy/ProxySQL containers have not been successfully restarted, a hard stop must be performed so that the master HAProxy/ProxySQL container with the faulty configuration is not also stopped and restarted.
loadbalancer: fail on failed "Wait for backup * to start" handlers
If a faulty HAProxy/ProxySQL configuration is applied and the backup HAProxy/ProxySQL containers have not been successfully restarted, a hard stop must be performed so that the master HAProxy/ProxySQL container with the faulty configuration is not also stopped and restarted.
Closes osism/issues#483