Added support for std::mutex in folly Deterministic Schedule

Added support for std::mutex in folly Deterministic Schedule

Summary:
Added the class `DeterministicMutex`, a wrapper for `std::mutex`, in `folly/test/DeterministicSchedule.h`. Added a test to `folly/test/DeterministicScheduleTest.cpp` to test the correct behavior of `DeterministicMutex` functions and that deterministic schedule is able to detect race conditions that involve `DeterministicMutex`.

Note: Bootcamp task

Reviewed By: djwatson

Differential Revision: D3412579

fbshipit-source-id: c12861c4ec1cfeadcef027be4513e8e4cb7e0176