[lib] reverse conditional logic for convertOpsToClientDBOps in message store ops

Summary: In the next diff I will introduce the logic to handle the local field in the message store using the ops approach. As a preliminary step to this introduction, I needed to reverse this logic here so that I can add additional conditions in the next diff.

Test Plan: Confirmed that there are no regressions with message store + tested the entire stack at the end of the hackathon

Reviewers: tomek, kamil, will

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12214