Description of problem:
When I have an external auth source of type Active Directory, on its Account tab, I can check Use Netgroups checkbox but Submitting doesn't save this setting. The setting is not applied and the next time I visit that tab, it's unchecked again.

Version-Release number of selected component (if applicable):
Sat 6.14 snap 3.0, not a regression

How reproducible:
Deterministic

Steps to Reproduce:
1. Administer -> Auth Sources -> LDAP -> Create
2. On the first tab, fill connection data and select Active Directory as Server type
3. On the second tab, fill account data and check Use Netgroups.
4. Submit
5. Open the new auth source details and go to Account tab

Actual results:
Use Netgroups is not checked

Expected results:
Since Use Netgroups seems not to be supported for AD, the checkbox shouldn't be visible or it should be greyed-out

Additional info:
Caused by https://github.com/theforeman/foreman/blob/develop/app/models/auth_sources/auth_source_ldap.rb#L199