Don't wait for finishing animation when second display is disconnected

Basically WindowManagerService wait for finishing animation when
a window is removed. But when second display is disconnected, windows
on second display can't be shown even if animation is waited for.
On the contrary, it keeps on waiting for finishing the animation
in special case.

With this fix windows are immediately removed without waiting for
animation when second display is disconnected.

Change-Id: I1354c193c04db394a21a11c174e10c8e7da17a0e