Use a bool for ForceDefaults instead of an int

The actual function takes a bool.

While we are doing this, add a couple missing ForceDefaults.

Change-Id: I7fd41c048dae340ca4f339230ceb033349db0faf
diff --git a/aos/events/event_loop.h b/aos/events/event_loop.h
index 4294226..27df016 100644
--- a/aos/events/event_loop.h
+++ b/aos/events/event_loop.h
@@ -252,7 +252,7 @@
           allocator_(allocator),
           sender_(sender) {
       CheckChannelDataAlignment(allocator->data(), allocator->size());
-      fbb_.ForceDefaults(1);
+      fbb_.ForceDefaults(true);
     }
     Builder() {}
     Builder(const Builder &) = delete;