fixes #6445 - Configure external authentication via FreeIPA.
fixes #6445 - Addressing (most of the) build warnings.
fixes #6445 - WARNING: string containing only a variable.
fixes #6445 - Prior to RHEL 6.6, httpd_dbus_sssd is unavailable.
fixes #6445 - Avoid using $ as variable start.
fixes #6445 - Be conditional for SELinux-related operations.
fixes #6445 - Using foreman::config::passenger::fragment.
fixes #6445 - Using apache::mod for module loading.
fixes #6445 - Fixing access to facts.
fixes #6445 - Only do the external authentication setup if passenger is used.
fixes #6445 - ipa-getkeytab cones from ipa-client which is expected on IPA-enrolled machine.
fixes #6445 - with mod_lookup_identity-selinux (as an httpd_dbus_sssd workaround), SELinux can be Enforcing.