Added test connection action to all data sources, Closes #1997

public/app/plugins/datasource/opentsdb/datasource.js

@@ -90,6 +90,12 @@ function (angular, _, kbn) {
       });
     };
 
+    OpenTSDBDatasource.prototype.testDatasource = function() {
+      return this.performSuggestQuery('cpu', 'metrics').then(function () {
+        return { status: "success", message: "Data source is working", title: "Success" };
+      });
+    };
+
     function transformMetricData(md, groupByTags, options) {
       var metricLabel = createMetricLabel(md, options, groupByTags);
       var dps = [];