[Buildbot] #3015: bulletproof component activation

[Buildbot trac]

#3015: bulletproof component activation
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Reporter:  dustin       |      Owner:
    Type:  enhancement  |     Status:  new
Priority:  major        |  Milestone:  0.9.0
 Version:  0.8.9        |   Keywords:
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 In #3012 Ben ran into trouble with a poller that won't activate because
 it's already recorded as active in the DB.  We should be more aggressive
 about checking for active masters and deactivating components on those
 masters when the masters are down.

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Ticket URL: <http://trac.buildbot.net/ticket/3015>
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