Tests: never use System.err

Always print stack traces to System.out, and replace all
System.err.println()'s with System.out.println().

Follow-up of https://android-review.googlesource.com/#/c/187020/ and
https://android-review.googlesource.com/#/c/407032/.

Test: m test-art-host
      m test-art-target
Change-Id: I9ab9cd955a8db25b2ec6673790e5bc924f62c88a
diff --git a/test/142-classloader2/src/Main.java b/test/142-classloader2/src/Main.java
index a0c7764..193fd5d 100644
--- a/test/142-classloader2/src/Main.java
+++ b/test/142-classloader2/src/Main.java
@@ -91,7 +91,7 @@
           if (e.getCause() instanceof VerifyError) {
             System.out.println("Caught wrapped VerifyError.");
           } else {
-            e.printStackTrace();
+            e.printStackTrace(System.out);
           }
         }