[Merge] lp:~sjakthol/update-manager/fix-slow-calculation into lp:update-manager

[Michael Terry]

Sami, love the work.  Thank you so much!

60	+ if callable(eventloop_callback) and random.random() < 0.01:

I'm a little uncomfortable using random().  What about if (len(self._deps) % 1000 == 0) or something similar?
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https://code.launchpad.net/~sjakthol/update-manager/fix-slow-calculation/+merge/161284
Your team Ubuntu Core Development Team is requested to review the proposed merge of lp:~sjakthol/update-manager/fix-slow-calculation into lp:update-manager.