Clear "task did not complete" warning when an error occurs

[phated]

Ref gulpjs/gulp#2168

[another-guy]

The false negatives (Did you forget to signal async completion?) reported by @MLoughry in the ref'ed issue is occurring to me to. I'm too talking specifically about the gulp.parallel(failingTask, notFailingTask) case.

Since the ref'ed issue has been closed, is this the right issue to subscribe for status notification(s)?