[Buildbot] #3429: Rename 'slave' to 'agent'

[Buildbot trac]

#3429: Rename 'slave' to 'agent'
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Reporter:  forschler  |      Owner:
    Type:  undecided  |     Status:  new
Priority:  major      |  Milestone:  undecided
 Version:  0.8.12     |   Keywords:
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 We've had complaints of using the word 'slave' in our build
 infrastructure, as it can be considered offensive. We should consider
 changing them to less offensive options.  We could use BuildAgent instead
 of BuildSlave.

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Ticket URL: <http://trac.buildbot.net/ticket/3429>
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