Expire dying parent from threading cache before processing children

Fixes a crash in the Model when a thread leader is removed and
ViewJob for its children is started to re-attach the subtree
to a new parent node. The second pass would then get a pointer
to the now-deleted parent from the threading cache leading to
a crash eventually.

This patch makes sure the parent is expired from the cache
before the ViewJobs are started. The cache miss triggers actual
threading calculation in Pass2 and Pass3 and updates our cache.

BUG: 364994
FIXED-IN: 16.08.1