Call JNI_OnUnload when class loaders get collected

Added test case to 141-class-unload.

Bug: 22720414
Change-Id: I0575fae72521520a17587e8b0088bf8112705ad8
diff --git a/test/051-thread/expected.txt b/test/051-thread/expected.txt
index 54e34af..c6cd4f8 100644
--- a/test/051-thread/expected.txt
+++ b/test/051-thread/expected.txt
@@ -1,3 +1,4 @@
+JNI_OnLoad called
 thread test starting
 testThreadCapacity thread count: 512
 testThreadDaemons starting thread 'TestDaemonThread'