[Merge] lp:~xnox/upstart/shrink-notifications into lp:upstart

[Dimitri John Ledkov]

Backed out jodh's merged tests.
Made tests resilient to tests (pass 100+ iterations).

Fixed races:
- sigchild ariving, before read handler is called

Fixed aborts:
- due to multiple io reads, since process_fd pipe was not cleared
- job_process_error_handler returning EILSEQ
- double freeing io, when read handler is called before close handles
-- 
https://code.launchpad.net/~xnox/upstart/shrink-notifications/+merge/225200
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