Fix run-libcore-tests exclusions for fugu.

Don't include libcore_debug_failures.txt on fugu debug.
as it has duplicate entries with libcore_fugu_failures.txt.

This is odd, but it is what the bash script used to do.

Change-Id: Ia7ebf48ac84f4f7b08f8868345c61e1207cd0e04
diff --git a/tools/run-libcore-tests.py b/tools/run-libcore-tests.py
index 19aeb13..c120cb3 100755
--- a/tools/run-libcore-tests.py
+++ b/tools/run-libcore-tests.py
@@ -136,7 +136,7 @@
       failures.append("art/tools/libcore_gcstress_failures.txt")
     if args.gcstress and args.debug:
       failures.append("art/tools/libcore_gcstress_debug_failures.txt")
-    if args.debug and not args.gcstress:
+    if args.debug and not args.gcstress and args.getrandom:
       failures.append("art/tools/libcore_debug_failures.txt")
     if not args.getrandom:
       failures.append("art/tools/libcore_fugu_failures.txt")