base

Add a missing case when detecting if a toast can be added

We allow only one toast window per UID to be added at a
time. We ignore windows that run exit animation but we
should also ignore windows that should be removed after
the exit animation.

bug:31340854

Change-Id: I51c21f2c0e04341697f61e4cc107f9116254b206
(cherry picked from commit 62a40f87b3f45cbd20fea101d977153e9a933891)