[BEAM-3133] Add logging when Staging takes a long time

[tgroh]

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[coveralls]

Coverage decreased (-0.01%) to 70.506% when pulling c43b2ca on tgroh:log_during_staging into 71196ec on apache:master.

[reuvenlax]

@tgroh any update?

[aaltay]

@tgroh Is this PR still relevant?

[tgroh]

It's very low priority, but I think it's still an improvement.

[reuvenlax]

If we're not going to finish this soon, let's close the PR. We can always reopen the PR later.

[reuvenlax]

Please associate a JIRA issue with this as well.

[tgroh]

R: @kennknowles

[tgroh]

retest this please