Update role grant flow to be synchronized

The current role grant is an async task and we don't wait until it's
finished before sending the callback to the app. It casuses the issue that the onAssociationCreated callback is returned before the role is granted.

Fix: 251625222

Test: CTS & build
Change-Id: Ie5b2331ec4b25af8d2e7bd8b5c1ab88245440a74