SnackBarManager state is not cleared when SnackBar is detached from a
window without dismiss(). After then it is remained as dismissing state
forever.
Test: 1) Long-press a conversation and click archive action.
2) Press back key before the snackbar is dismissed.
3) Repeat 1) and check the snackbar is shown or not.
Change-Id: Icf2cdcd30aea42685db68e5ac36436a34c9c94ae
Signed-off-by: Taesu Lee <taesu82.lee@samsung.com>
aa23161c03