I recognized this behavior with our current 4.0-3 VirtualBox VM: If you choose to join an Active Directory Domain, although there is non, you will get the error message that no AD DC could be found with the configured DNS settings. If you close this message and then choose not to set up any domain, the summary page will show that the software component Active Directory Domain is chosen.
This should be fixed with Bug 37333. I removed the logic that auto-selects the AD connector. Instead, the AD connector is auto-installed if AD member mode is selected. *** This bug has been marked as a duplicate of bug 37333 ***