Summary:
Without this change about half of the updaterandom reads and merge puts will be for keys that don't exist.
I think it is better for these tests to start with a full database and use fillseq to fill it.

Task ID: #

Blame Rev:

Test Plan:
Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D35043