Add simple wait for the A11yService to shut down in Bug_386950836.

This host side test does not have access to smarter waiting logic
like checking AccessibilityManager#getEnabledAccessibilityServiceList,
so perform a simple sleep instead.

Fix: 409405107
Test: run in go/abtd
Flag: EXEMPT test only
Change-Id: Ie1bb8ee4a135f794f35d699b063fd0ee7b6569bf
1 file changed