ipa-otptoken-import: open the key file in binary mode
    
    ipa-otptoken-import provides an option (-k KEYFILE) to import
    an encrypted PSKC file but this option does not work with python3
    in RHEL8 and above, because the key should be passed in binary
    format to the cryptography functions instead of string format.
    
    Open the keyfile in binary mode to pass the expected format.
    
    Fixes: https://pagure.io/freeipa/issue/9609
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>