LDAP: Change the default rfc2307 autofs attribute mappings
    
    Resolves:
        https://fedorahosted.org/sssd/ticket/2858
    
    The default attribute mappings we used to have:
        ldap_autofs_map_object_class        automountMap
        ldap_autofs_map_name                ou
        ldap_autofs_entry_object_class      automount
        ldap_autofs_entry_key               cn
        ldap_autofs_entry_value             automountInformation
    
    Was wrong. Instead, this patch switches to:
        ldap_autofs_map_object_class        nisMap
        ldap_autofs_map_name                nisMapName
        ldap_autofs_entry_object_class      nisObject
        ldap_autofs_entry_key               cn
        ldap_autofs_entry_value             nisMapEntry
    
    Which are attributes that are available with servers running the default
    rfc2307 schema. In addition, this patch adds a syslog and DEBUG message
    that warns administrators to double-check their configuration.
    
    We don't warn when the autofs provider is set to AD, because that one
    is already correct.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>