Optimize deferrable mode execution for DataprocSubmitJobOperator

[phanikumv]

This PR verifies if a dataproc job has already completed (or) errored out (or) cancelled before deferring the task to prevent unnecessary deferring. This way, we can skip deferring the task if it has already been finished.

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[hussein-awala]

I don't know what is the probability to have a quick end of the job like that regardless the reason, we are talking about a few microseconds after the submission 🤔

Is there any issue/use case which can be fixed/covered by this PR?

[dstandish]

Shouldn't this only be in the defer path? Otherwise it would seem it is duplicative.

And then might be nice to shove this code into a private method too.

e.g.

        if self.deferrable:
            job_id = self._check_before_defer(...)
            if job_id:
                return job_id
            self.defer(
                trigger=DataprocSubmitTrigger(

[phanikumv]

moved the code under self.deferrable condition