server install: require IPv6 stack to be enabled
Add checks to install and replica install to verify IPv6 stack
is enabled. IPv6 is required by some IPA parts (AD, conncheck, ...).
https://pagure.io/freeipa/issue/6608
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>