Prevent duplicate certificates in TrustedCertificateIndex
Chad Brubaker authored
With the separate caching of intermediate certificates in
TrustManagerImpl a given intermediate may be passed into .index multiple
times. Avoid adding the certificate to the list each time.

(cherry-picked from commit d080e064)
Bug: 26232830
Change-Id: I6bed2c65d9e42e052b9b1b129200a997e7dca745
4c9f9c22