Toggle mutex locks. Setting do_lock to a zero value causes
Berkeley DB to grant all requested mutual exclusion mutexes without regard
for their availability.
This functionality should never be used for any other purpose than
debugging.
The DbEnv::set_mutexlocks interface may be used to configure Berkeley DB at any time
during the life of the application.
The DbEnv::set_mutexlocks method either returns a non-zero error value or throws an exception that
encapsulates a non-zero error value on failure, and returns 0 on success.