Fix virtual display power state management.

Before:
 - setSurface results in OFF/ON display state, ignoring the relevant
   power group state.

After:
 - display states follow the relevant power group state.
 - setSurface can turn off and on the display if the power group is
   on but has no effect if the power group is off. This is in line
   with the API docs of VirtualDisplay#setSurface

Fix: 369061926
Test: CTS
Flag: EXEMPT bugfix
Change-Id: Iff0b59ba400c7eb1277a2bd65e835b715215a8b6