SERVER-14668: Use SimpleMutex instead of SpinLock for LockManager

There can be contention on these, so spin locks are not appropriate.
SERVER-15777 findAndModify shouldn't explicitly create WriteUnitOfWork
SERVER-15797 doTTLForIndex shouldn't explicitly create WriteUnitOfWork
SERVER-15707 Fix C++11'ism and a long line
Merge remote-tracking branch 'upstream/master'