NIFI-3061 PutAzureEventHub blocks after network interruption

[jfrazee]

This change maintains status quo and does not enable the existing unit tests. The change was tested against NIFI-3061.xml though. As mentioned in NIFI-3070, there isn't a good way to provide meaningful unit tests so integration tests should be added as a new improvement.

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[ijokarumawak]

Reviewing...

[ijokarumawak]

I've confirmed the upgrade works without problem using my Azure environment. +1, merged into master.
I agree with the idea of improving integration test. Thank you, @jfrazee !!