Roll tools/swarming_client/ to 02196398776eff7d735a499e21cd644d5c3faf91.

$ git log a57d7db40..021963987 --date=short --format='%ad %ae %s' | sed 's/@chromium\.org//'
2014-10-17 maruel Add --idempotent support now that the server supports it.
2014-10-17 maruel Fix a client side failure when a task completely blows up.

TBR=vadimsh@chromium.org
BUG=

Review URL: https://codereview.chromium.org/666673008

Cr-Commit-Position: refs/heads/master@{#300492}

DEPS

@@ -56,7 +56,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling swarming_client
   # and whatever else without interference from each other.
-  'swarming_revision': 'a57d7db4026bca8e0fab9aadd4953503e8d74e74',
+  'swarming_revision': '02196398776eff7d735a499e21cd644d5c3faf91',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling ANGLE
   # and whatever else without interference from each other.