bigtable.hbase.async.TestAsyncColumnFamily: testAddColumn failed

[flaky-bot]

Note: #3037 was also for this test, but it was closed more than 10 days ago. So, I didn't mark it flaky.

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commit: f244ff9
buildURL: Build Status, Sponge
status: failed

[flaky-bot]

Looks like this issue is flaky. 😟

I'm going to leave this open and stop commenting.

A human should fix and close this.

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When run at the same commit (f244ff9), this test passed in one build (Build Status, Sponge) and failed in another build (Build Status, Sponge).