Update ipa-server-install man page for hostname
Hostname is always set, remove the text that says
hostname is set only if it does not match the current
hostname.
https://fedorahosted.org/freeipa/ticket/6330
Reviewed-By: Abhijeet Kasurde <akasurde@redhat.com>
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>