Don't rely on having an oplog in tests.
Don't rely on having an oplog in tests.

Travis doesn't, for one, but also most developer machines won't
necessarily either.

stripe/mosql,maheshm/mosql,NewAmsterdamLabs/mosql,ojosdegris/mosql,marty-stranger/mosql,mmasashi/mosql,jperichon/mosql,ackinc/mosql