Fix path to AVF debug policy in the DT

The avf node contains sub nodes that are not debug-related. Change it to avf/guest to not be affected by those sub nodes.

Bug: 345118393
Change-Id: Icc8e36082cfe256bfdd2ce3e5bba258ef3442544
Test: run the test with husky-user
diff --git a/tests/hostside/java/com/android/microdroid/test/MicrodroidHostTests.java b/tests/hostside/java/com/android/microdroid/test/MicrodroidHostTests.java
index 9d0b04b..80d1fc6 100644
--- a/tests/hostside/java/com/android/microdroid/test/MicrodroidHostTests.java
+++ b/tests/hostside/java/com/android/microdroid/test/MicrodroidHostTests.java
@@ -1038,7 +1038,7 @@
         assumeFalse("Unlocked devices may have AVF debug policy", lockProp.equals("orange"));
 
         // Test that AVF debug policy doesn't exist.
-        boolean hasDebugPolicy = device.doesFileExist("/proc/device-tree/avf");
+        boolean hasDebugPolicy = device.doesFileExist("/proc/device-tree/avf/guest");
         assertThat(hasDebugPolicy).isFalse();
     }