Manage redirectToWake state in DreamOverlayService.

Previously, DreamOverlayService required an active dream client in order
for redirectToWake to be set. The overlay implementation might want to
set this state before a dream is actually running or between dreams.
This change handles setting redirectToWake outside of an active dream.

Test: atest DreamOverlayServiceTest#testRedirectToWakeAcrossClients
Fixes: 361804879
Flag: EXEMPT bugfix
Change-Id: Ia88b33d63464ed5ab244eb13192c1cdc7061fa39