Disable MSAN for MicroLock functions
Disable MSAN for MicroLock functions

Summary: Even though `folly::MicroLock` is 1 byte, `detail::Futex<>` (aka `std::atomic<uint32_t>`) operates on 4 bytes. So 3 bytes are accessed but not used in any way. So we need to disable memory sanitizer.

Reviewed By: andriigrynenko

Differential Revision: D26082888

fbshipit-source-id: fe585b60c96f48c02df69d182bd75a8eccde2a42

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