be consistent about .override use

disabling of service is correct, but checking whether
it is disabled is not

upstart service is disabled by creating {service-name}.override file
and adding a 'manual' stanza there [1]

[1] http://upstart.ubuntu.com/cookbook/#disabling-a-job-from-automatically-starting
Merge pull request #5252 from kvbik/disabling-upstart-job

be consistent about .override use