OpenSSLCipher: multiple calls to updateAAD were ignored

Do to a missing assignment statement, only the first call to updateAAD
was honored and the rest were discarded.

(cherry picked from commit a23b05b327b9d8fefc44276c2fa80278ef210c0f)

Bug: 27371173
Change-Id: I77ad7800b0905f72d5abe76b56352a94056ceb9c
