[server] Skip updates in changeRole if no change detected
[server] Skip updates in changeRole if no change detected

Summary: We check this in the other permissions updaters, so I figured we might as well do it in `changeRole` as well.

Test Plan: Will be tested in combination with following diffs

Reviewers: palys-swm, atul

Reviewed By: palys-swm

Subscribers: KatPo, Adrian

Differential Revision: https://phabricator.ashoat.com/D1365

Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal