Summary:
db_stress test is now failing because of this scenario
- run db_stress with merge_operator enabled (now we have a db with merge operands)
- run db_stress with merge_operator disabled (now when we fail to open the db)
the solution is to pass the merge_operator to the DB even if we are not going to do any merge operations
Test Plan: Check the failure
Reviewers: andrewkr, yiwu, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D61311