Add a small comment to a test

Addresses comments on aosp/1771187

Test: comment-only change
Change-Id: I837a019708919b66b8801c37abd5aacb1d7c249f
diff --git a/tests/unit/java/com/android/server/ConnectivityServiceTest.java b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
index 46d680c..8f79fc7 100644
--- a/tests/unit/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
@@ -2206,6 +2206,7 @@
         deathRecipient.get().binderDied();
         // Wait for the release message to be processed.
         waitForIdle();
+        // After waitForIdle(), the message was processed and the service didn't crash.
     }
 
     @Test