Suppress URLErrors when uploading metrics.

These can just be from not having a network connection.

Bug: 887540
Change-Id: Ie025cc278a4633d688bfb34544ecaaacb2df1bad
Reviewed-on: https://chromium-review.googlesource.com/1236893
Auto-Submit: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>

upload_metrics.py

@@ -15,6 +15,8 @@ def main():
     urllib2.urlopen(metrics_utils.APP_URL + '/upload', metrics)
   except urllib2.HTTPError:
     pass
+  except urllib2.URLError:
+    pass
 
   return 0