[JENKINS-25406] Downgrade ISE to log warning

[jglick]

JENKINS-25406

Under circumstances yet to be identified, the Maven plugin sometimes tries to set the build result after the build is COMPLETED, which is illegal. Until 1.586 Jenkins core silently let it do so unless you happened to be running with -ea. As of 1.587 this becomes an IllegalStateException, which alerted us to the problem but might be breaking more important things (unclear what the impact is). Downgrading this to a warning in the log and just ignore the attempt to change the build result.

@reviewbybees

[KostyaSha]

Shouldn't break anything, so 👍

[jglick]

Could break something, in case the Maven plugin was really relying on being able to change build status after completion.

Build timed out on CI. I will set the project to use a faster machine class and will file a separate PR for an unrelated test failure.

[KostyaSha]

@jglick then lets comment return and grab logging results first?

[jglick]

(now subsumes #41)

[jglick]

lets comment return and grab logging results first

I am not sure what that would tell us. We already have the stack traces, and they do not point to a clear culprit. Need a way to reproduce the problem.

[jglick]

Hmm, for some reason PR builds do not seem to be being triggered at all ATM.

[KostyaSha]

@jglick push slowly 😆

[tfennelly]

👍 looks fine to me

[jenkinsadmin]

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