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/044-proxy/src/Clash3.java b/test/044-proxy/src/Clash3.java
index 44806ce..9d23059 100644
--- a/test/044-proxy/src/Clash3.java
+++ b/test/044-proxy/src/Clash3.java
@@ -35,7 +35,7 @@
                     Interface3aa.class,
                     Interface3b.class },
                 handler);
-            System.err.println("Clash3 did not throw expected exception");
+            System.out.println("Clash3 did not throw expected exception");
         } catch (IllegalArgumentException iae) {
             System.out.println("Clash3 threw expected exception");
         }