[server] Make sure we update parentThreadID in updateRole before updating permissions
[server] Make sure we update parentThreadID in updateRole before updating permissions

Summary:
Permissions depend on the `parentThreadID`, and the SQL queries in `thread-permission-updaters.js` depend on the `parent_thread` column. Consequently, we should make sure we update this column before calculating a `MembershipChangeset`.

It's not currently possible in the UI to change a thread's parent thread, but I figured I would make this change for correctness's sake.

Test Plan: This only matters if `updateThread` changes the thread's parent thread, which isn't currently possible in the UI, so this one is hard to test. I'm content that the extensive testing I did for the other diffs in this series would've caught any serious issues

Reviewers: palys-swm

Reviewed By: palys-swm

Subscribers: KatPo, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D1026

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