[Core] Utilize sys.exit in configcheck

[nmuesch]

Note: Please remember to review the Datadog Contribution Guidelines
if you have not yet done so.

What does this PR do?

Utilizes the sys.exit() function in the configcheck command utility. This allows the exit code to be determined based on whether or not the yaml configs are good/bad.

Motivation

Customer Request. Now when running the one off config check script/command, you can utilize $? to determine if there are any bad yaml files.

Previously, if the configcheck finished and printed that there were errors in the yaml files, the following command:

echo $?

would output `0. Now this outputs 1, indicating there was a failure.

Testing Guidelines

An overview on testing
is available in our contribution guidelines.

Additional Notes

Anything else we should know when reviewing?

[olivielpeau]

This fix makes a lot of sense, thanks!

I think the current behavior is actually a regression that was introduced way back in #1422.

I don't think exiting directly from the configcheck option is great though, there might be other callers of this function that just want to check if the configs are valid without exiting the process if they're not.

The caller of configcheck should use the returned value of the function and exit with that value if it makes sense to exit. Does that make sense?

[olivielpeau]

Getting better, added one comment on the current changes

[olivielpeau]

sd_configcheck doesn't return anything so I don't think it makes sense to have it in the condition here. I'm not sure we could make that function return a sensible value that reflects the status of the service discovery confs...

So instead of this, I think we should simply make this code return the value that configcheck returns. The part of the code under __main__ will then exit with the correct status code.

[olivielpeau]

Thanks @nmuesch! Merged, this should be included in 5.17.0