Fix goma_artifacts output proto update for stats/counterz.

Add info logging around stats/counterz file copying.

BUG=chromium:1013499
TEST=run_tests

Change-Id: I08046d1915f1c31691ff089e11c2ec80f5b78778
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2020465
Tested-by: Michael Mortensen <mmortensen@google.com>
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
diff --git a/api/controller/sysroot.py b/api/controller/sysroot.py
index 95244e5..a1f892b 100644
--- a/api/controller/sysroot.py
+++ b/api/controller/sysroot.py
@@ -185,7 +185,7 @@
     if archiver_tuple.stats_file:
       output_proto.goma_artifacts.stats_file = archiver_tuple.stats_file
     if archiver_tuple.counterz_file:
-      output_proto.goma_artifacts.stats_file = archiver_tuple.counterz_file
+      output_proto.goma_artifacts.counterz_file = archiver_tuple.counterz_file
     output_proto.goma_artifacts.log_files[:] = archiver_tuple.log_files
 
   # Read metric events log and pipe them into output_proto.events.