Return non-zero on "microk8s status" when service is stopped

[rsalinas]

Summary

microk8s status returns 0 when the server is down.

$ microk8s status --yaml ; echo $?
microk8s is not running, try microk8s start
0

What Should Happen Instead?
I would expect it to return non-zero, so that I don't need to search for text in the output.

This also complicates my life when trying to directly parse its output as yaml.
Closes #3974

Changes

It returns 1 instead of 0 when the server is down.

Testing

I DID NOT TEST MY CHANGES.
Please someone adopt this tiny change and test it for me :)

Possible Regressions

Checklist

• Read the contributions page.
• Submitted the CLA form, if you are a first time contributor.
• The introduced changes are covered by unit and/or integration tests.

Notes