only dupe check when needed

Only enable datum dupe checking in collection after data
has been received.  This works under the assumption that a
single telemetry request will not contain duplicate elements,
thus, it is not necessary to check for dupes on the initial
request.

Improves performance when rows are sorted by a column
that has duplicate row-values.

platform/features/table/src/controllers/TelemetryTableController.js

@@ -292,6 +292,7 @@ define(
                  */
                 function finishProcessing() {
                     telemetryCollection.add(rowData);
+                    telemetryCollection.dupeCheck = true;
                     scope.rows = telemetryCollection.telemetry;
                     scope.loading = false;
 
@@ -377,6 +378,7 @@ define(
             function newData(domainObject, datum) {
                 limitEvaluator = telemetryApi.limitEvaluator(domainObject);
                 added = telemetryCollection.add([table.getRowValues(limitEvaluator, datum)]);
+                this.telemetry.dupeCheck = true;
             }
 
             objects.forEach(function (object) {