Fixing #703 : missing ContentType header on datatable invoker api

components/device-mgt/org.wso2.carbon.device.mgt.ui/src/main/resources/jaggeryapps/devicemgt/api/data-tables-invoker-api.jag

@@ -62,6 +62,7 @@ if (uriMatcher.match("/{context}/api/data-tables/invoker")) {
             function (backendResponse) {
                 response["status"] = backendResponse["status"];
                 response["content"] =  utility.encodeJson(backendResponse["responseText"]);
+                response["contentType"] = "application/json";
             }
     );
 }