crypto-tests: Rename encrypt decrypt test case
    
    libsss_crypto provide 2 pairs of encrypt + decrypt functions.
    sss_password_encrypt + sss_password_decrypt and more generic
    sss_encrypt + sss_decrypt.
    
    The name of one test case was a little bit confusing.
    It evokes that different pair of functions were tested.
    
    Reviewed-by: Christian Heimes <cheimes@redhat.com>
    (cherry picked from commit 96d239e83e671b82525cec760cf0bcaa5ee1c249)