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/159-app-image-fields/src/Main.java b/test/159-app-image-fields/src/Main.java
index d06a502..47d0116 100644
--- a/test/159-app-image-fields/src/Main.java
+++ b/test/159-app-image-fields/src/Main.java
@@ -57,7 +57,7 @@
                 System.out.println("another_value: " + another_value);
             }
         } catch (Throwable t) {
-            t.printStackTrace();
+            t.printStackTrace(System.out);
         }
     }