manager: kill procs in parallel (#23010)

* manager: kill procs in parallel

* oops block
old-commit-hash: ba67c355db

selfdrive/manager/manager.py

@@ -102,8 +102,13 @@ def manager_prepare():
 
 
 def manager_cleanup():
+  # send signals to kill all procs
   for p in managed_processes.values():
-    p.stop()
+    p.stop(block=False)
+
+  # ensure all are killed
+  for p in managed_processes.values():
+    p.stop(block=True)
 
   cloudlog.info("everything is dead")