Bigtable/ReadModifyWriteRowInterceptorMetrics: should record and export correct metrics for ReadModifyWriteRow via interceptors failed

[flaky-bot]

This test failed!

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If I'm commenting on this issue too often, add the flakybot: quiet label and
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commit: 9744aa3
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 (9744aa3), this test passed in one build (Build Status, Sponge) and failed in another build (Build Status, Sponge).