OpenSSLCipher: reset AAD when necessary

AAD was not being reset correctly during init or doFinal calls thus
leading to incorrect output.

(cherry picked from commit 0bab7f3b89ea13eb0d0c39d9c7b60c6112f0d6a8)

Bug: 27324690
Change-Id: If7806a9d7847814b60719637abceb94d8fbc8831
