LogDog: Actually use default max buffer age.

LogDog: Actually use default max buffer age.

The documentation for the MaxBufferAge parameter suggests that if it's
zero, a default value will be used. However, this was not actually
implemented. Historically this has not been a problem, since the only
user always supplied a non-zero value, but now that Butler is being
used elsewhere as a library, let's fix this.

TBR=hinoka@chromium.org
BUG=chromium:628321
TEST=None

Committed: https://github.com/luci/luci-go/commit/ac277ae13b4b040d504162c4dc6f6bd08de5149e

[dnj, 2016-07-18 19:24:58]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2016-07-18 19:24:59]

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, 2016-07-18 19:45:10]

Description was changed from

==========
LogDog: Actually use default max buffer age.

The documentation for the MaxBufferAge parameter suggests that if it's
zero, a default value will be used. However, this was not actually
implemented. Historically this has not been a problem, since the only
user always supplied a non-zero value, but now that Butler is being
used elsewhere as a library, let's fix this.

TBR=hinoka@chromium.org
BUG=chromium:628321
TEST=None
==========

to

==========
LogDog: Actually use default max buffer age.

The documentation for the MaxBufferAge parameter suggests that if it's
zero, a default value will be used. However, this was not actually
implemented. Historically this has not been a problem, since the only
user always supplied a non-zero value, but now that Butler is being
used elsewhere as a library, let's fix this.

TBR=hinoka@chromium.org
BUG=chromium:628321
TEST=None

Committed:
https://github.com/luci/luci-go/commit/ac277ae13b4b040d504162c4dc6f6bd08de5149e
==========

[commit-bot: I haz the power, 2016-07-18 19:45:11]

Committed patchset #1 (id:1) as
https://github.com/luci/luci-go/commit/ac277ae13b4b040d504162c4dc6f6bd08de5149e