Allows starting window to be shown for swipe-dismiss windows.

This change removes the hack in WindowManagerService which
prevented a starting window from being created for a window with
the swipe-to-dismiss flag set.  Per the comment in the file, a
starting window is not created for translucent windows (which a
swipe-to-dismiss window implicitly is) because the translucency
of the window interacts poorly with the default entry transition;
this does not apply to swipe-to-dismiss windows as they use a
different entry transition.

Removing this allows us to start the transition before the app
has finished drawing its UI (showing the app's theme's
default background drawable as suggested in
https://spec.googleplex.com/quantum/patterns/launch-screens.html)
which makes app launching on Wear much more responsive.

Bug: 23066614
Change-Id: I99b85aeb9a9fcce277239b6f430691c3abf86177