compositor: Release ds_surface_viewport when ds_surface is destroyed

compositor: Release ds_surface_viewport when ds_surface is destroyed

This is to fix abort by calling ds_surface_viewport_release() after
ds_surface has been destroyed.

The listeners added using e_surface_destroy_listener_add() have been
called in a hook handler E_CLIENT_HOOK_DEL, which is emitted when
e_object_del() is called for the associated E_Client. However, if
e_object_delay_del_ref() is called for the E_Client, the listeners for
E_CLIENT_HOOK_DEL would not be called immediately. Instead, it is
called when delay_del_ref count is dropped to zero by calling
e_object_delay_del_unref().

This means that listeners of e_surface_destroy_listener_add() can be
called after ds_surface is already freed, and the call to
ds_surface_viewport_release() in this case causes undefined behavior.

Change-Id: Ie8f316b2aef841c89386a41f19a4f5066d98d9bc