IPA_ACCESS: Make hbac_get_cache_rules() more generic
    
    This method can also be reused in the future for new backend modules.
    
    In order to make it more generic, let's just move it to
    ipa_rules_common.[ch], rename it to ipa_common_get_cached_rules() and
    make the rule, subtree name and the attributes to be searched new
    parameters of this method.
    
    In order to not be declaring the enourmous list of attributes HBAC uses
    when calling this method, a new hbac_get_attrs_to_get_cached_rules()
    method has been introduced.
    
    Related:
    https://pagure.io/SSSD/sssd/issue/2995
    
    Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>