LogDog: Properly emit Butler stream magic.

LogDog: Properly emit Butler stream magic.

The LogDog Butler protocol was not properly implemented: it was missing
the magic byte sequence that must precede the exchange. Add that
sequence to the stream implementation.

BUG=chromium:628770
TEST=local
  - Ran with live Butler instance, observed successful stream
    negotiation.

Committed: https://github.com/luci/luci-py/commit/999aff1abdcaf37cfed37f7451ea0a2f54a7fdea

[dnj, 2016-08-19 02:42:57]

dnj@chromium.org changed reviewers:
+ martiniss@chromium.org

[dnj, 2016-08-19 02:42:57]

PTAL

[martiniss, 2016-08-19 17:24:00]

lgtm

[dnj, 2016-08-19 20:37:58]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2016-08-19 20:38:06]

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, 2016-08-19 21:11:10]

Description was changed from

==========
LogDog: Properly emit Butler stream magic.

The LogDog Butler protocol was not properly implemented: it was missing
the magic byte sequence that must precede the exchange. Add that
sequence to the stream implementation.

BUG=chromium:628770
TEST=local
  - Ran with live Butler instance, observed successful stream
    negotiation.
==========

to

==========
LogDog: Properly emit Butler stream magic.

The LogDog Butler protocol was not properly implemented: it was missing
the magic byte sequence that must precede the exchange. Add that
sequence to the stream implementation.

BUG=chromium:628770
TEST=local
  - Ran with live Butler instance, observed successful stream
    negotiation.

Committed:
https://github.com/luci/luci-py/commit/999aff1abdcaf37cfed37f7451ea0a2f54a7fdea
==========

[commit-bot: I haz the power, 2016-08-19 21:11:11]

Committed patchset #1 (id:1) as
https://github.com/luci/luci-py/commit/999aff1abdcaf37cfed37f7451ea0a2f54a7fdea