SERVER-29802, we can run multiple applyOps on the same server concurrently if we use
and apply only CRUD. In this mode, applyOps() uses MODE_X to lock the database before calling applyOperation_inlock(). This does not take advantage of storage engines that support document level concurrency.
This ticket proposes to relax the locking rules in applyOps() to use MODE_IX instead of MODE_X when applying CRUD-only workloads non-atomically.