[Merge] lp:~xnox/upstart/bug-1199778 into lp:upstart

[Dmitrijs Ledkovs]

This started off as:
https://code.launchpad.net/~jamesodhunt/upstart/bug-1199778/+merge/174138

Fixing assert in stateful re-exec, when there are active chroot sessions.

But that was not enough, as a stateful re-exec still did not complete and upstart was falling back to stateless re-exec. This is due to a mapping error between deserialised job_classes and json_job_classes at the last-pass dependency resolution. In essence, whilst chroot session job_classes were skipped at de-serialisation, the resolution stage did not account for those skipped classes and expected a 1-to-1 sequential mapping between job_classes and json_job_classes.

Also see:
https://bugs.launchpad.net/upstart/+bug/1200264
https://bugs.launchpad.net/upstart/+bug/1199778
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https://code.launchpad.net/~xnox/upstart/bug-1199778/+merge/174372
Your team Upstart Reviewers is requested to review the proposed merge of lp:~xnox/upstart/bug-1199778 into lp:upstart.