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/050-sync-test/src/ThreadDeathHandler.java b/test/050-sync-test/src/ThreadDeathHandler.java
index 0a7437d..58061f8 100644
--- a/test/050-sync-test/src/ThreadDeathHandler.java
+++ b/test/050-sync-test/src/ThreadDeathHandler.java
@@ -27,7 +27,7 @@
     }
 
     public void uncaughtException(Thread t, Throwable e) {
-        System.err.println("Uncaught exception " + mMyMessage + "!");
-        e.printStackTrace();
+        System.out.println("Uncaught exception " + mMyMessage + "!");
+        e.printStackTrace(System.out);
     }
 }