Unlock the device before running a StartupTest benchmark (#112243)

diff --git a/dev/devicelab/lib/tasks/perf_tests.dart b/dev/devicelab/lib/tasks/perf_tests.dart
index 9e5fb80..85bfcec 100644
--- a/dev/devicelab/lib/tasks/perf_tests.dart
+++ b/dev/devicelab/lib/tasks/perf_tests.dart
@@ -655,6 +655,7 @@
   Future<TaskResult> run() async {
     return inDirectory<TaskResult>(testDirectory, () async {
       final Device device = await devices.workingDevice;
+      await device.unlock();
       const int iterations = 5;
       final List<Map<String, dynamic>> results = <Map<String, dynamic>>[];