No error message for SolrCollector if no cores are present #661

When ever we add the solrcollector for solr 5.5.4 or 6.6.0 in diamond, the diamond service starts with out any message on the terminal or logs. But the solr server metrics are not visible in the graphite dashboard. No error message is displayed in the logs. This is because no cores are present in the solr server. If we add one then the metrics start to load in the graphite dashboard.
Diamond version used is: 4.0.809
Graphite version: 0.9.0
The solrcollector should display a proper message.