Deflake NotificationTemplateViewWrapperTest

Test passes 100% in isolation (and is quite simple) but is extremely flaky when run in the suite. So I'm guessing it's caused by the sUiOffloadThread being cached before it's set to the testable one (on the first usage from somewhere else). So force a refresh here.

Fixes: 444085872
Fixes: 443062831
Test: atest NotificationTemplateViewWrapperTest
Flag: TEST_ONLY
Change-Id: Iab00d848e79377e419e9c8d369f5e70107392de7