Description of problem:
When doing a host install without user authentication (options --noac and
-S/--no-sssd), requirement of ldap authentication modules is kind of
superfluous

Version-Release number of selected component (if applicable):
ipa-client-3.0.0-42.el6.x86_64

How reproducible:
always

Steps to Reproduce:
1. make sure you don't have nss_ldap or nss-pam-ldap packages installed
2. call ipa-client install with all user authentication options disabled
(--noac, -S)
3.

Actual results:
ipa-client-install complains about missing packages:
One of these packages must be installed: nss_ldap or nss-pam-ldapd
Installation failed. Rolling back changes.

Expected results:
The packages are required only when needed

Additional info:
if some of these packages are always required, it might be worthy to consider
them a packaging dependency