Thumbor metrics not visible if --processes argument set

[VladVolchkov]

Hi, I faced exactly same behaviour as @sktoiva described in #14. I couldn't reproduce it locally until noticed that in EKS I'm setting --processes 4 launch argument. Metrics appeared after this launch argument was removed for testing purposes, but anyway I need it and just wondering is it a bug or just additional configuration required?

#16 can fix issue, but changes need to be validated, as I'm not an expert in this area

[savar]

Thanks you again for your contribution and sorry again for the delay. The package can be found here.

Please see the CHANGELOG and README.md for documentation.

As I didn't want to wait this out for too long, I kind of rushed this a bit. Please open another issue and/or PR in case you find any errors on the code, tests or documentation.

In case you are happy with this, please close the issue.