[server] Fix up logic in updateThread to handle thread parent requirements

Summary: Noticed this was broken

Test Plan: didn't have time to test :( careful reading and Flow

Reviewers: subnub, palys-swm

Reviewed By: palys-swm

Subscribers: KatPo, zrebcu411, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D784