Back out "folly: cmake: enable DistributedMutexTest.cpp"
Back out "folly: cmake: enable DistributedMutexTest.cpp"

Summary:
I only enabled this speculatively, but since it quite a heavyweight
test, it is timing out in the open source build, so let's turn it off again.

Reviewed By: lewissbaker

Differential Revision: D14817162

fbshipit-source-id: 343b021890974e5b92975bdfc7b4fa554d20a703

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