Call JNI_OnUnload when class loaders get collected

Added test case to 141-class-unload.

Bug: 22720414
Change-Id: I0575fae72521520a17587e8b0088bf8112705ad8
diff --git a/test/137-cfi/expected.txt b/test/137-cfi/expected.txt
index e69de29..6a5618e 100644
--- a/test/137-cfi/expected.txt
+++ b/test/137-cfi/expected.txt
@@ -0,0 +1 @@
+JNI_OnLoad called