This is only a test fix.

lock_stats_suboperation_curop.js and lock_stats_suboperation_logs.js don't work with mobile storage engine because

1. There is only one level of locking so we can't use currentOp() (which takes a global S lock) to capture an in-progress index build (which takes a global X lock).
2. The assumption that parent operation and the sub-operation have the same lock waiting time seems to be affected by noise very easily.