Catch RemoteDisconnected on upload metrics

It's possible that remote closes connection, which would result in a
stacktrace being shown in the stderr. Silence this exception, as we do
with other exceptions.

R=gavinmak@google.com

Bug: 1328518
Change-Id: Ifae2aca64fe5d572c0b71008f6dacbb63ba77e06
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3664178
Reviewed-by: Gavin Mak <gavinmak@google.com>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>

upload_metrics.py

@@ -3,6 +3,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import http
 import os
 import sys
 import urllib.error
@@ -22,7 +23,8 @@ def main():
         url=metrics_utils.APP_URL + '/upload',
         data=metrics.encode('utf-8'),
         headers=headers))
-  except (urllib.error.HTTPError, urllib.error.URLError):
+  except (urllib.error.HTTPError, urllib.error.URLError,
+          http.client.RemoteDisconnected):
     pass
 
   return 0