[FIX] registry: prevent inherited phantom cache clears

This patch complements the previous one by ensuring that any
`cache_invalidated=True` flag inherited from the master process
(pre-fork mode) cannot trigger a cache clear.

This could occur when the first request is served, because the flag was
never clear in the master process, which never server any request.

At the end of `check_signaling()`, the local cache has either been
cleared because a (real) increment of the cache sequence was detected,
or it is considered still valid. The final state of the
`cache_invalidated` flag should reflect this, by being `False`.

closes odoo/odoo#65303

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>