[Buildbot] #3275: nextSlave should be able to choose slave according to "build request"

[Buildbot trac]

#3275: nextSlave should be able to choose slave according to "build request"
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Reporter:  nam4dev    |      Owner:
    Type:  undecided  |     Status:  new
Priority:  major      |  Milestone:  undecided
 Version:  master     |   Keywords:
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 Based on Pull request (buildbot-eight):
 https://github.com/tardyp/buildbot/commit/5ed2131f1debc5810ec6c3d6da26e33963657cf7

 buildbot-nine too, should allow to choose slave from the `BuildRequest`
 instance.

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Ticket URL: <http://trac.buildbot.net/ticket/3275>
Buildbot <http://buildbot.net/>
Buildbot: build/test automation