Don't use "no border" property to determine if Deleted was decorated

With xdg-toplevel windows, the value of the "no border" property can be
sometimes out of sync with the fact whether the window is decorated. This
may result in Deleted windows being frameless.

In order to address that issue, we need to store the current value of
AbstractClient::isDecorated() during the construction of Deleted.


(cherry picked from commit ed5dfa16)