Must provide syslog properties even if disabled [fixes #215]

Until https://github.com/cloudfoundry/cf-release/pull/113 is merged, we must provide
`properties.syslog_aggregator.host` even if its not enabled; otherwise bosh
may not be able to apply templates.
Merge pull request #216 from cloudfoundry-community/syslog

Must provide syslog properties even if disabled [fixes #215]