Refresh tiles on user change

Post a stale tile when the user changes (right after), this will force
tiles to do a refresh and update the UI, preventing leaking old info.

Test: manual
Test: atest QSTileImplTest
Bug: 361770993
Flag: EXEMPT bugfix
Change-Id: Ief989e939d099d531f9d20d7b61847cd92bf7eed