scheduler-perf: inject "benchmark" as name into JSON result filename

This is required because an empty name is no longer supported: the
perf-dashboard is run with --allow-parsers-matching-all-tests=false with causes
perfdash to skip current configuration for BenchmarkPerfResults as it does not
have name
set (4674704f45/perfdash/metrics-downloader.go (L165-L167)).

The perf-dash config needs to be updated accordingly.

test/integration/scheduler_perf/scheduler_perf_test.go

@@ -724,7 +724,7 @@ func BenchmarkPerfScheduling(b *testing.B) {
 			}
 		})
 	}
-	if err := dataItems2JSONFile(dataItems, b.Name()); err != nil {
+	if err := dataItems2JSONFile(dataItems, b.Name()+"_benchmark"); err != nil {
 		b.Fatalf("unable to write measured data %+v: %v", dataItems, err)
 	}
 }