Make global callbacks usable outside appengine.

Make global callbacks usable outside appengine.

This moves the ResetGlobalCallbackMetrics call inside tsmon's Flush, and adds
a InvokeGlobalCallbacksOnFlush that defaults to true but is set to false on
appengine.

BUG=706912
Review-Url: https://codereview.chromium.org/2795613002
Committed: https://github.com/luci/luci-go/commit/82564cfcaebd57e7d65bb40997a050538a9845b8

[dsansome, 2017-04-03 03:07:43]

dsansome@chromium.org changed reviewers:
+ sergeyberezin@chromium.org

[Sergey Berezin (google), 2017-04-03 20:59:53]

sergeyberezin@google.com changed reviewers:
+ sergeyberezin@google.com

[Sergey Berezin (google), 2017-04-03 20:59:54]

LGTM, thanks!

[dsansome, 2017-04-03 23:30:55]

The CQ bit was checked by dsansome@chromium.org

[commit-bot: I haz the power, 2017-04-03 23:31:05]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-03 23:48:22]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1491262255541480, "parent_rev":
"806b8e8c8ae0181f36135f796ecfc58d54f79cea", "commit_rev":
"82564cfcaebd57e7d65bb40997a050538a9845b8"}

[commit-bot: I haz the power, 2017-04-03 23:48:27]

Description was changed from

==========
Make global callbacks usable outside appengine.

This moves the ResetGlobalCallbackMetrics call inside tsmon's Flush, and adds
a InvokeGlobalCallbacksOnFlush that defaults to true but is set to false on
appengine.

BUG=706912
==========

to

==========
Make global callbacks usable outside appengine.

This moves the ResetGlobalCallbackMetrics call inside tsmon's Flush, and adds
a InvokeGlobalCallbacksOnFlush that defaults to true but is set to false on
appengine.

BUG=706912

Review-Url: https://codereview.chromium.org/2795613002
Committed:
https://github.com/luci/luci-go/commit/82564cfcaebd57e7d65bb40997a050538a9845b8
==========

[commit-bot: I haz the power, 2017-04-03 23:48:28]

Committed patchset #1 (id:1) as
https://github.com/luci/luci-go/commit/82564cfcaebd57e7d65bb40997a050538a9845b8