Always returns exit code 0 in CLI mode

[MichalKrasowski]

Regards Linux OS.
Returns 0 even if the subtitles were unavailable.
Different exit codes could be useful for scripting.

User story:

1. Try to download subs for non-existent movie:
   $ qnapi -c movie.avi &> /dev/null && echo ok || echo no
2. Script returns
   no

[krzemin]

There were different return codes for different scripting results, but for this case (non-existing file) there was a bug, causing 0 return code.

Thanks for reporting, now it's fixed.