Roll src/tools/swarming_client/ 7f463e66e..b6e9e23e4 (4 commits)

https://chromium.googlesource.com/infra/luci/client-py.git/+log/7f463e66e1c4..b6e9e23e4e79

$ git log 7f463e66e..b6e9e23e4 --date=short --no-merges --format='%ad %ae %s'
2018-11-20 maruel [client]: fix undefined class reference
2018-11-19 vadimsh [proto] Fix google/rpc/*_pb2.py, it has wrong proto paths in it.
2018-11-19 maruel protobuf: upgrade to 3.6.1 from 3.5.1
2018-11-19 jchinlee [client] Print time with tasks update message. Also increase frequency.

Created with:
  roll-dep src/tools/swarming_client

R=jchinlee@chromium.org

Bug: 905012
Change-Id: I5e397d787e27223d94dd85b35d3c2826dc93febe
Reviewed-on: https://chromium-review.googlesource.com/c/1343666Reviewed-by: Jao-ke Chin-Lee <jchinlee@chromium.org>
Commit-Queue: Marc-Antoine Ruel <maruel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609845}

DEPS

@@ -120,7 +120,7 @@ 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': '7f463e66e1c4bb830ef3de9d046aa227d28e1b00',
+  'swarming_revision': 'b6e9e23e4e79249bd4f95735205ffb7c3f9f0912',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling ANGLE
   # and whatever else without interference from each other.