Revert "YARN-2977. Fixed intermittent TestNMClient failure. (Contributed by Junping Du)"

This reverts commit d79f63120e16cb03f3f85b5d79a84202881a95a5.
Revert "CHANGES.txt: add YARN-2977"

This reverts commit 3419091631777ec04dd1a9e2bf24adab2496c5ce.