DO NOT MERGE Work around for use-after-free cert bug

Cherry pick from master, SHA:
  95b2bad159f2dbca0555e82f156db8424b75c2b8

Holds a strong references in the cert cache.
This is a simpler alternative to full backport of upstream fix,
from http://crrev.com/92977 -- see bug for more details.

BUG: 6508448
Change-Id: Ic8182c267653216bbcafe466ecfe1951bf6a292a
3 files changed