Upstart configuration should use 'expect stop' for compatibility with Collectd v5.5+

[alowde-catapult]

Collectd version >= 5.5 automatically recognises that it's supervised by Upstart based on the UPSTART_JOB environment variable, and attempts to signal Upstart by raising SIGSTOP instead of forking.

Unfortunately this means that if Upstart is configured with 'expect fork' as per 9481210 then when the service is started Upstart will hang indefinitely.

Using 'expect stop' instead will allow Upstart to recognise that Collectd has started and, as a bonus, when it has finished initialising.