Test modeld: 3s enough for modeld startup (#29936)

* Test modeld: 3s enough for modeld startup

* Always fails when you send frames before modeld is ready

* Wait for modeld to read

selfdrive/modeld/tests/test_modeld.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-import time
 import unittest
 import numpy as np
 import random
@@ -27,8 +26,7 @@ class TestModeld(unittest.TestCase):
     self.pm = messaging.PubMaster(['roadCameraState', 'wideRoadCameraState', 'liveCalibration', 'lateralPlan'])
 
     managed_processes['modeld'].start()
-    time.sleep(0.2)
-    self.sm.update(1000)
+    self.pm.wait_for_readers_to_update("roadCameraState", 10)
 
   def tearDown(self):
     managed_processes['modeld'].stop()