If syslog_aggregator running, properties host/port required

If syslog_aggregator job template is running then deployment file should provide:

    properties:
     syslog_aggregator:
       host: 0.syslog_aggregator.default.mydeployment.bosh
       port: 54321

If syslog_aggregator job template is not running, then do not specify `properties.syslog_aggregator` at all.