+++ This bug was initially created as a clone of Bug #1811546 +++

Description of problem:
LDAP backend default doesn't align to keystone defaults.

For example, use_pool and use_user_pool is false in puppet-keystone.
However, keystone's default configuration is true.

Also there are so many undef assignment to the parameters.

This is also found at upstream puppet-keystone.

Version-Release number of selected component (if applicable):
Current puppet-keystone

How reproducible:
Always

Steps to Reproduce:
1. Try to configure ldap backend.
2. Check keystone.conf.
3.

Actual results:
Some parameters aren't same as keystone's default.

Expected results:
Not assigned parameters by T-H-T should be the same as keystone's defaults.

Additional info:

--- Additional comment from Dave Wilde on 2020-03-18 18:35:24 UTC ---

We have proposed the following patches [0], [1] to the master branch of puppet-keystone to default to upstream keystone defaults as well as to deprecate certain parameters which no longer appear in keystone.  The new undef parameters in the ldap_backend.pp file will use the upstream keystone defaults if they are not specifically overridden:

# This is an example template on how to configure keystone domain specific LDAP
# backends. This will configure a domain called tripleoldap will the attributes
# specified.
parameter_defaults:
  KeystoneLDAPDomainEnable: true
  KeystoneLDAPBackendConfigs:
    tripleoldap:
      url: ldap://192.168.24.251
      user: cn=openstack,ou=Users,dc=tripleo,dc=example,dc=com
      password: Secrete
      suffix: dc=tripleo,dc=example,dc=com
      user_tree_dn: ou=Users,dc=tripleo,dc=example,dc=com
      user_filter: "(memberOf=cn=OSuser,ou=Groups,dc=tripleo,dc=example,dc=com)"
      user_objectclass: person
      user_id_attribute: cn
      use_pool: false
      use_auth_pool: false

[0]: https://review.opendev.org/#/c/713708/
[1]: https://review.opendev.org/#/c/713712/