Make sure to have storage space for tag
    
    ber_scanf expects a pointer to a ber_tag_t to return the tag pointed at
    by "t", if that is not provided the pointer will be store in whatever
    memory location is pointed by the stack at that time causeing a crash.
    
    Note that this is effectively unused code because in ipa-kdb the only
    party that can write a key_data structure to be stored is te kdb_driver
    itself and we never encode these s2kparam data.
    
    But we need to handle this for future proofing.
    
    Fixes #8071
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>